Evolt

"I'm the game maker. I derive the best strategy by considering every possibility. Everything is going as planned."

- Blood Stalk's speech to Night Rogue. "Even if I had never come to Earth, you people would've found yourselves causing another war soon enough. I remember telling you this before. Science always ends up causing destruction! Scientific advancement makes life more convenient, and people start to take things for granted. Before they know it, they will find themselves embroiled in war. That's the future...that science promises!"

- Evol's speech to Build.

Blood Stalk is one of the leaders of the organization Faust and the primary antagonist of Kamen Rider Build. He initially appears as a subordinate of Night Rogue, though is eventually revealed to be manipulating both the villains and the heroes towards his own goal of constructing the Pandora Tower and using it to wipe out all life on Earth.

His true identity is Evolt, a mysterious entity who annihilated the ancient civilization on Mars long ago using the power of the Pandora Box. He took over the body of Soichi Isurugi, owner of the cafe nascita and secretly the astronaut who discovered the Pandora Box 10 years ago, and used him to trigger the Skywall Disaster that separated Japan.

Evolt eventually obtains back the Evol Driver, granting him the power to transform into Kamen Rider Evol. From their, Evolt completes the Evol Trigger and uses it to assume his Black Hole form, the form with which he used to annihilate Mars. Evolt then begins working to complete the Black Pandora Panel with the 10 Lost Fullbottles so he can absorb it to achieve his complete form.

In the movie Kamen Rider Build: Be The One, Evolt is revealed as a member of an enigmatic extraterrestrial clan known as the Blood Tribe who travel the universe devouring planets to increase their own power.

Blood Stalk/Evolt is voiced by Tetsuo Kanao. As Soichi Isurugi, Evolt is portrayed by Yasuyuki Maekawa.

Past
Hailing from an unknown planet home to the Blood Tribe, Evolt roamed the galaxy destroying countless worlds.

In the ancient past, Evolt used Pandora Box to create the Pandora Tower and annihilate the civilization of Mars with a massive distortion. To prevent him from moving on to other planets, Vernage, the Queen of Mars, fragmented Evolt's spirit from his body and sealed his power away in the Pandora Box.

Following the destruction of Mars, a fragment of Evolt's essence traveled to Earth with a Martian probe. After the probe was discovered, Evolt's essence entered the womb of a security guard for the probe, Yuri Banjou, and fused with her unborn son Ryuga. Ryuga was born a month later, containing the essence inside him though it did not influence his personality.

10 years prior to the events of Build, Soichi Isurugi, an astronaut working with the Kiwami Project, discovered the Pandora Box while on Mars. Soichi unwittingly released Evolt's consciousness and possessed by him. At the ceremony back on Earth, under Evolt's control, Isurugi applied his hand to the Pandora Box, causing the Sky Wall Disaster.

"Soichi" was later arrested and placed in a mental hospital, along with his daughter, Misora Isurugi, who was also exposed to the box and gained the ability to purify Fullbottles.

However, "Soichi" escaped about a month later and went to Shinobu Katsuragi to get him to invent the Lost Bottles and the Rider System. Searching for ideas for the 60 empty Fullbottles he had, Evolt probed Soichi's mind for the 30 Organic Fullbottles, with Soichi offering up things Misora liked such as animals. Evolt then asked Soichi for things that could destroy those 30 things to use for the 30 Inorganic Fullbottles, to which Soichi initially offered up tanks and other weapons, but later switched random things likes comics to avoid bringing harm to the things that Misora liked.

7 years later, he was appointed as a special consultant for the Pandora Box. He also co-founded Faust with Gentoku Himuro and Takumi Katsuragi as a way to carry out secret experiments to restore his former power, under the guise of improving the Touto military.

Under Faust
Misora later joined Faust to purify the Fullbottles for them, though she was unware at first of their true purposes. When she eventually found out about Faust's intentions, she lost her will to continue working for them. "Soichi" then "saved" her and took her back to the cafe, where he convinced her to continue purifying the bottles for good.

"Soichi" later stole the Pandora Box panels from the Touto Institute of Advanced Matter Physics to ensure their confidence and plastered into one of nascita's basement walls. He also took along a Build Driver and some Fullbottles from Faust.

Dealing with Katsuragi
When Takumi Katsuragi attempted to quit Faust, Blood Stalk knocked him out and switched his clothes and face with Taro Satou, whom Stalk had previously killed by Stalk. Stalk then left Taro Satou in the alleyway and erased Takumi's memories before talking him back to Faust to experiment on him. On September 5th, Isurugi brought the amnesiac Katsuragi to a small alleyway. After Takumi woke up, Soichi renamed him Sento Kiryu and nurtured him into Kamen Rider Build so that, with Build fighting more monsters, Soichi would have reasons to have Misora purify more bottles.

Encounters with Build
Blood Stalk was first seen by Build when he showed up to take Masahiro Nabeshima after he was reverted from his form as the Mirage Smash by Build. He injected Sento in the back with poison that left him stunned and unable to do anything while Stalk retrieved the unconscious Nabeshima.

Later, Stalk showed up again as Build was fighting the Square Smash. Stalk stood up from the park bench he was sitting on and fired a Devil Steam from his Steam Rifle at the Square Smash, causing it to grow giant. After observing Build fight and defeat the Smash, Stalk leaves and returns to Faust's lair. Night Rogue questions Stalk as to why he didn't kill Build, but Blood Stalk assures him that Build being left alive is all according to plan.

After discovering out Ryuga took Misora sightseeing outside nascita, Blood Stalk had Faust Guardians sent to their current location. He showed up as Ryuga was facing Night Rogue and Misora was passed out and told Rogue to not act behind his back. When Ryuga tried to flee with an unconscious Misora and fled, Night Rogue attempted to pursue him but was stopped by Stalk stopped him. Returning to Faust's lair, Stalk demanded Night Rogue to know why Rogue plotted behind his back. Rogue then informed Stalk that Faust's benefactor, Juzaburo Namba, president of Namba Heavy Industries Ltd. had asked to be given the Rider System and threatened to ally himself with either Hokuto or Seito if he did not receive it. As Rogue cancelled his transformation, Stalk asked Gentoku what he intended to do. Gentoku ultimately decided that they should steal the Pandora Box from the Touto Institute of Advanced Matter Physics in order to cause the three regions to declare war on each other.

Theft of the Pandora Box
The next day, Stalk and a squad of Faust Guardians waited in the garage level of the Touto Institute of Advanced Matter Physics. While Shingo Kuwata distracted Build, Eita Kawai disabled the security lock at the garage level, allowing Stalk and his Guardians to enter the Institute. Proceeding to the entrance floor, Stalk killed the four security officers stationed there by injecting them with a poison that disintegrated them. He then had Kawai trap the three Prime Ministers, Nariaki Utsumi, two security officers and the Pandora Box in an energy dome until he reached the floor where the box was located. Pursued by Touto Guardians and Touto Special forces, Stalk converted the Touto Guardians into Faust Guardians and went on his way. As he reached the eleventh floor, the dome dispersed, allowing Stalk to proceed toward the Pandora Box. He killed the two security officers with his poison before telling the Prime Minsters that he'll be taking the Pandora Box. Prime Minister Yoshiko Tajimi of Hokuto attempted to defy Stalk, but Stalk caused her to back down by threatening her with his Transteam Gun before using it to destroy the security cameras.

Making his way to the roof with the Pandora Box, Stalk was approached from behind by Ryuga, disguised as a Touto Security officer. Praising Ryuga for his boldness, Stalk had his Faust Guardians engaged Ryuga, but Ryuga defeated all of them with the power of his Dragon Fullbottle. Intrigued by Ryuga's power, Stalk attempted to fight him until Kawai showed up and told Stalk to leave Ryuga to him. Obliging, his request, Stalk used his Steam Blade to infuse Kawai with Devil Steam and turn him into a Press Smash Hazard and leaving Ryuga to fight the Smash. On the rooftop, Stalk was confronted by Gentoku, who told Stalk the roof wasn't in their escape route. Stalk told him he was lost, Gentoku was unconvinced and commented on how Stalk had shot out the security cameras to cover his tracks. Transforming into Night Rogue, he demanded Stalk hand over the box, but Stalk refused. Rogue then engaged Stalk until Ryuga showed up and interrupted their fight. Stalk asked him what had happened to the Smash, to which Ryuga informed him that he beat it but couldn't extract the Smash element without an empty Bottle, surprising Rogue and impressing Stalk.

Ryuga then attacked Stalk, but was swiftly defeated due to the injuries he sustained from his previous fight with the Press Smash Hazard. Build HawkGatling then arrives to help him, prompting Rogue to assist Stalk against them. While Rogue fought Build, Stalk battled Ryuga. Stalk soon discovered that Ryuga's Hazard Level has risen to 3.0, and commended him for finally awakening his full power, though it still wasn't enough to beat him. As Stalk overpowered Ryuga, Build FireHedgehog ceased fighting Rogue and attacked Stalk. Rogue then used the opportunity to sneak-attack Build, giving Stalk the chance to insert his Cobra Fullbottle into his Steam Rifle and fire a Steam Shot at both Rogue and Build, knocking Rogue to a wall and cancelling Build's transformation as well as causing him to drop the majority of his Fullbottle collection. Stalk takes the Pandora Box and leaves.

Returning to the ground floor, Stalk finds the Press Smash Hazard and defeats it and extracts the Smash element from it, reverting it back to Kawai. As Stalk left, Kawai questioned Stalk if he was Takumi Katsuragi, suggesting that the Devil's Scientist had faked his death, but Stalk denies his claims. Kawai refused to believe him and stated that Katsuragi could've used modern technology to transfigure a corpse. Stalk then approached Kawai and demonstrated his ability to do so, painfully molding Kawai's face into Kuwata's. As Sento rushed to an unconscious Kawai, Stalk fused with a Faust Guardian Union State and fled. Pursued by Build RabbitTank, Stalk shot at Build to get him off his trail. However, Build managed to destroy one of the Union State's legs before finishing it off with the Machine Builder's axle saw, forcing Stalk out of the Union State.

Having overheard Stalk's conversation with Kawai, Sento questioned Stalk as to why he faked his death, framed Ryuga and injected Sento with the Nebula gas, but Stalk asked Sento if that's what he should really be asking. Sento then asked him why he created Faust, the Smash, and if the Rider System was a tool to protect the innocent. Stalk replied by knocking Sento down and telling him the Rider System was a military weapon for bloodshed, telling him science leads to destruction. Refusing to believe Stalk's claims, Sento states that if used properly, science can bring people happiness. Night Rogue then appears and knocks Sento out from behind. Having his Faust Guardians circle them and point their rifles at Stalk, Rogue questions Stalk about where he intended to take the Pandora Box. Stalk tells him that he was going to take it to their lair, offering Rogue the box. Taking the box, Rogue grabs Stalk to threaten him to not try a stunt like that again, before stealing the Rabbit, Tank and Lion bottle from an unconscious Sento. As Sento returned to consciousness, he grabbed Rogue's leg, demanded he return his bottles, but Rogue just kicks him in the face before walking away laughing.

Betrayal of Night Rogue
After Gentoku refused to reveal the location of the Pandora Box due to Stalk's treachery, Stalk began searching for the box on his own, eventually tracking it to the Namba Heavy Industries Integrated Science Laboratory. Stalk skirmished with both Sento and Ryuga and Night Rogue before teleporting away with the Box.

After Gentoku disbanded Faust to cover his tracks, he discovered that Juzaburo Namba had dropped Gentoku as a partner and instead partnered up with Blood Stalk.

His true identity was eventually discovered by Build and Ryuga after they defeated him in a fight and cancelled his transformation. His cover blown, Isurugi revealed to the two that Gentoku was Night Rogue and allowed them to keep the Green Panels and the Pandora Box.

Rebuilding Faust
Blood Stalk later rebuilt Faust within Hokuto and temporarily aligned with them, providing them with the resources they needed to engineer Smash and the schematics for the Sclash Driver, allowing them to to create Kamen Riders. With former farm owner Kazumi Sawatari as their test subject, Blood Stalk and Faust used him to create Kamen Rider Build. They also developed a new form of Smash called Hard Smash, who were capable of retaining their consciousness in their Smash transformation. Stalk and Faust turned three farm workers of Kazumi's into Hard Smash, and they would come to be known as the Hokuto Three Crows.

Working with Namba
Stalk later switched over to working with Seito when they invaded and conquered Hokuto with backing from Namba Heavy Industries Ltd. He converted a now banished Gentoku Himuro into Kamen Rider Rogue so he could be used as the Kamen Rider of Seito.

After Seito lost a proxy battle with Touto and thus had to relinquish the Fullbottles and Pandora Box as per their agreement, Blood Stalk was summoned by Namba to kill Seito's Prime Minister Masakuni Mido and swap their faces so Namba could take control of Seito.

Becoming Evol
Stalk later attempted to get Sento and Ryuga to hand over the Evol Driver so he could regain his long lost power. The two were ready to deliver the Driver to Stalk, but chose not to and fought off Stalk with assistance from Kamen Rider Rogue. After being soundly defeated by the Riders, Stalk attempted to retreat but was chased down and knocked out of his transformation by Rogue. However, thanks to the actions of Nariaki Utsumi, Evolt managed to gain the Evol Driver and transform into Kamen Rider Evol. Overpowering Rogue, Evol prepared to finish Gentoku off but his attack was blocked by Gentoku's father Taizan.

Completing the Pandora Box
"The time is finally here. Taste the despair!"

- Evol as he constructs the Pandora Tower.

Eventually, Evol possesses Ryuga and obtains all of the panels of the Pandora Box and uses them to assemble it and use it to create the Pandora Tower to destroy Earth. Horrified, Juzaburo Namba sends Nariaki Utsumi out to go stop him, but Evol simply shoots him away with the Nebulasteam Gun. He then laughs as the Pandora Tower is completed, declaring that "Earth is finished".

Evol then uses the Pandora Box to create the Evol Trigger, the device that allowed him to destroy Mars, but discovers that the body of Ryuga is not strong enough to use it. He is then ambushed by Vernage possessing Misora, who knocks him against a wall before teleporting away with Sento and the Pandora Box. She then explains to Sento, Kazumi and Gentoku who Evolt is and how he annihilated all life on Mars.

Back at Seito's capital, Evol claims to Namba and Utsumi that he created the Pandora Tower to showcase Namba's power to the world. Though unnerved, Namba goes along with Evol's explanation. Evol is later seen in Ryuga's body leading a Seito on Touto before Build steps in to fight him. Transforming into Evol Dragon, Evol and Build fight, and Evol reveals to Build that the whole point of Project Build was to create someone strong enough to harness the energy of the Evol Trigger. Discovering that Build has raised his power to superhuman levels, Evol abandons Ryuga as a host and tries to possess Sento, but Sento reveals this was his plan all along and attempts to kill both Evol and himself by rapidly raising his Hazard Level until he overclocks. However, Sento's plan fails and Evol succeeds in claiming Sento as a host, much to Ryuga's horror when he wakes up.

Possessing Sento
Ryuga attempts to transform into Kamen Rider Cross-Z to fight Evol Rabbit, but Evol reveals that he removed all of his alien DNA from Ryuga's body when he exited it and that without it, he cannot transform into a Kamen Rider. Kamen Rider Grease then tries to attack Evol, but Evol effortlessly beats him down and cancels his transformation before leaving. Meeting with Namba, Evol reveals his true origins to the war profiteer, but claims he only wants to regain his former power.

Evolt later arranges a meeting with Ryuga Banjou and Kazumi Sawatari, promising to return Sento to them if they hand over the Pandora Box. At the meeting spot, Evolt notices that he is being accompanied by Engine Bro's and Remocon Bro's, who were sent by Namba to keep an eye on him. After Ryuga and Kazumi arrive, Evolt reveals that he has no intention of letting Sento go, as revenge for him impeding the progress of his plans. He leaves the two to be fought by the two Kaisers, not considering them worthy of being taken care of by himself, though he does interfere in the battle when Grease starts to gain the upper hand.

However, after Kamen Rider Rogue appears and defeats Remocon Bro's and Engine Bro's, Evolt decides to enter the battle himself. Transforming into Evol Cobra, Evol engages Rogue and manages to overpower him after switching to Evol Rabbit. During the battle, unknown to Evol, Ryuga managed to snatch the Dragon Fullbottle off of Evol's belt. He then attacks Evol untransformed and somehow manages to inflict damage upon him. Shocked, Evol questions how he is able to do that without his DNA inside of him. Ryuga then uses the Dragon Fullbottle to transform into Cross-Z and then Cross-Z Magma before engaging Evol alongside Kamen Riders Grease and Rogue. The three combine their energies for a final attack against the Kamen Rider, but Evol manages to absorb their energies and use them to transform into his final form, Evol Black Hole, setting Sento free in the process.

Black Hole
"Phase 4... complete!"

- Evolt after assuming his Black Hole form.

Assuming his true form, Evol congratulates the Kamen Riders on helping him re-achieve his true powers, declaring that nothing can stop him now. The three Kamen Riders then attack Evol, but he manages to effortlessly fight them all off, forcing them to retreat back to nascita.

Taking the form of Soichi Isurugi, Evolt approaches Namba and declares his intent to supplant Namba Heavy Industries as the country's ruler, though offers to let him keep his spot as Prime Minister. Namba refuses, but Evolt decides to give him a day to think it over. He later approaches Nariaki Utsumi and proposes that he come work for him, complimenting his skills as a scientist. He then reveals to Utsumi a second Evol Driver.

The next day, Evolt is approached by Nariaki Utsumi, Remocon and Engine Bro's and a squad of Hard Guardians. Utsumi pulls out a tablet and from it, Namba declares his refusal to go along with Evolt's plans. Unfazed, Evolt assumes his form as Black Hole and teleports everyone present to a barren battlefield for them to fight at. The Hard Guardians all charge at Evol, but the alien destroys them all at once with only a fraction of his power. The Washio brothers then try attacking Evol, but they fair little better and are easily beaten down. However, backup soon arrives in the form of Kamen Riders Build, Cross-Z, Grease and Rogue, who all attempt to take on Evol again. Despite the best efforts of the Riders and Kaisers, Evol proves too powerful for them and eventually announces his intention to finish things, using his Black Hole finisher to kill Rai Washio.

Using his brother's Fullbottle to assume Hell Bro's, Fu Washio charges at Evol in a fierce attack to take him down, which fails. Before he can be killed however he is saved by Cross-Z Magma, who attempts to fight off Evol to little success. Forcing Ryuga out of his transformation, Evol prepares to finish him off, but Ryuga is pushed out of the way at the last second by Hell Bro's, who absorbs the attack instead. Forced out of his transformation by the attack, Fu Washio also dies, but not before proclaiming how nice it was to fight for someone else's sake.

Evol then opens a portal to Juzaburo Namba's office and goes to kill him. Namba pleads for Evol to spare his life, offering up his company to him if he lets him live. Amused by Namba's cowardice, Evol declares that he loves how disgusting humans are and gives Namba a hug, only for him to kill Namba right afterword by causing him to disintegrate.

Evol then returns to the battlefield and restates his offer to Nariaki Utsumi, tossing him Namba's cane. Believing that since Namba is dead now nothing matters, Utsumi accepts Evol's offer, causing Evol to laugh and declare that he doesn't even want to destroy Earth anymore. Evol tosses Utsumi the second Evol Driver and Utsumi uses it to transform into a Kamen Rider, with Evol declaring him to be "Kamen Rider Mad Rogue".

Conquering Japan
Back at the Pandora Tower, Evol informs Nariaki that he will be assuming the identity of Masakuni Mido now that Namba's dead and that they will be seizing control of Touto and reuniting Japan, stating that it will make things easier in the long run. Utsumi then asks Evol what he intends to do about the Kamen Riders, to which Evol replies that he intends to still keep on using them to further his goals, instructing Utsumi to bring them to him alive. Admiring his Evol Driver, Utsumi inquires to Evol where the second one came from, as he had previously believed their to only be one, but Evol coldly warns him to keep his questions to himself.

After Mad Rogue was defeated by Build Genius Form, Evolt arrived and noted he was previously unaware of the existence of the Genius Bottle before punching Kazumi, stealing the Hokuto Three Crows' Lost Bottles from him and teleporting away with Mad Rogue. Back at Faust's lab, Evolt reveals to Utsumi that he intends to use the Lost Bottles to turn humanity into the final form of Smash, Lost Smash, and have rampage and destroy each other. Utsumi then asks if this is why Evolt left the Kamen Riders alive, to which Evolt confirms his suspicions, commenting that he thinks they would make good Lost Smash.

Later, after Mad Rogue and Owl Lost Smash were defeated by Kamen Rider Build Genius Form and Grease, Kamen Rider Evol showed up in his Cobra Form to claim Kiba's Lost Bottle, stating that he intends to use it to create a new world. Evol then attacks and fights Build. After getting beat back by Build, Evol attempts to shift to his Black Hole form, but is stopped by Build, who proceeds to knock Evol out of his transformation. Complimenting Sento on the Genius Fullbottle, Evolt flees the scene to go back to Faust's base.

After Sento arranges a meeting with Shimizu Kyouichi, the first Strong Smash, Evol has Shimizu turn into a Lost Smash and attack Sento. After Build reverts him back to his original state with his Genius Form, Evol shows up as Black Hole Evol and kills Shimizu to keep him from providing Sento with any information, mocking Sento for being unable to save him. Evol Black Hole and Build Genius Form then fight, with Build managing to overpower Evol and beat him down with his Genius Finish. Proclaiming that he now understands the human emotion of anger, Evol fiercely attacks Build but is unable to do anything to his Genius Form. Evol then decides to just take the Fullbottles he's recovered and leave to go back to Faust's lab base.

Back at the base, Evolt converses with Shinobu Katsuragi, who notes that Evolt was acting more emotional than he usually does in his fight with Build. Evolt then informs Shinobu that they will have to speed up their timetable for their plans. As Shinobu completes another Lost Bottle, Evolt comments that they only have four more Bottles to go before they can "create a new world". Shinobu then asks Evolt why he killed Shimizu, as he was the last candidate they had to become a Lost Smash, to which Evolt informs him that Shimizu was spilling too much about their plans, and that they can use the Kamen Riders to create Lost Smash. Utsumi then walks in and Evolt tells him to speed up the production of Lost Smash before remarking that he has "a nation to unite".

Black Hole Evol then leads an attack on the Touto government office along with Kamen Rider Mad Rogue. While Mad Rogue and a pair of Hard Guardians fought Kamen Riders Cross-Z Magma and Grease, Evol faced off against Sento and Gentoku. Sento angrily asked Evol where his father was, but Evol pretended not to know. After fighting off Build Genius Form and Kamen Rider Rogue, Evol generated a black hole and used it to annihilate the Touto government office before departing along with Mad Rogue.

As Seito occupied Touto's territories, Evolt disguised himself as Masakuni Mido and gave a speech that was broadcasted across Touto, Hokuto and Seito, where he declared that he would unite the three territories and build a new Japan. After his speech is finished, Evolt tells Utsumi to procure the Kamen Riders so they can create Lost Smash from them. However, Utsumi points out that mass-producing Lost Smash and having them attack people would trigger the downfall of the nation and questions Evolt as to what he really wants, but Evolt tells Utsumi not to ask anymore questions about stuff he's not ready to know yet if he values his life.

Completing the Black Pandora Panel
After Utsumi was defeated by Kamen Riders Build Genius Form and Rogue, Evolt showed up along with Shinobu Katsuragi and revealed to the Riders that Shinobu had manipulated Sento and Ryuga into becoming Kamen Riders. Evolt then teleported away through a black hole with Utsumi, leaving Shinobu to fight the Riders.

Evolt later kidnapped Misora Isurugi so Shinobu could turn her into the CD Lost Smash by subjecting her to a high level of Nebula Gas. The CD Lost Smash was then released to fight Kamen Rider Build by Shinobu.

After Shinobu returned to Faust's base in Hokuto after being beaten by Build Genius Form and Cross-Z Magma, Evolt commented on how that was the first time he was wrong, to which Shinobu admits that he overestimated them. The two are then alerted by Nariaki Utsumi that Gentoku and Kazumi are attempting to infiltrate their base, to which Evolt states that "there's more fun to be had".

After Gentoku and Kazumi escape with help from Build and Cross-Z Magma, Evolt notes to Shinobu that he let them get away again, to which Shinobu replies by commenting on how strong they are. Later, Evolt calls Sento and tells him to hand over the Lost Bottle he retrieved from the CD Lost Smash, threatening to harm his family and friends if he refused.

Sento then goes to meet Black Hole Evol, but refuses to hand over the Lost Bottle. Ryuga, Kazumi and Gentoku then arrive to back up Sento, having tracked his position using a transmitter. The four then transform into their Kamen Rider forms and engage Black Hole Evol. Evol at first easily beats them down, but the Kamen Riders manage to gain the upper hand by having Rogue and Grease hold Evol while Cross-Z Magma disables the Evol Trigger, reverting Evol back to his Evol Cobra form. Build Genius Form then uses his Genius Finish on Evol and finishes off the evil Kamen Rider. Commenting that the Riders' fighting skills are "not bad", Evol tells the Riders that their fight is not over yet before exploding and seemingly dying, leaving behind three Lost Bottles. Shinobu as Build HawkGatling then swoops in and collects the Lost Bottles, telling the Riders that everything has gone exactly as he planned.

Return
Placing the Evol Driver inside a metal container to prevent Evolt from regenerating from the DNA he has inside it, Shinobu Katsuragi reveals that he was planning to stop Evolt all along, and only helped him out in order to complete the Black Pandora Panel, which would allow for warp travel between worlds. He states that Evolt sought to complete the panel because he could use it to making traveling from planet to planet easier and less time consuming.

Nariaki Utsumi then walks in and is revealed to be possessed by Evolt, who anticipated that Shinobu would betray him and sent some of his essence to possess Utsumi right before he was defeated. Evolt then kills Shinobu before transforming into Kamen Rider Mad Rogue with Utsumi's Evol-Driver and fighting Kamen Riders Cross-Z Magma, Grease and Rogue while Sento rushes over to his father. After fighting the Riders for a bit, Evolt remarks that Mad Rogue is limiting for him due to being fitted for a human, and discards Utsumi as a host before retrieving the Evol-Driver from the metal container and using it to transform into Kamen Rider Evol Cobra. Evol then retrieves the Black Pandora Panel and fights off the Kamen Riders, prompting them to retreat. Glancing at the panel, Evol remarks that he only needs one more Lost Fullbottle to complete it.

Later, as Masakuni Mido, Evolt implements a new form of government in Japan where Touto, Hokuto and Seito will each have regional governors and which will be based out of the Pandora Tower. He then stages an attack by Flying Clone Smash in order to lure out the Kamen Riders, save for Kazumi, who was injured in his last battle with Evolt.

Achieving his Complete Form
Confronting the Riders atop a rooftop, Evolt faces off against Sento, who attempts to use the Genius Bottle to transform into Build Genius Form, but finds he is unable to use it. Evolt reveals that he infected Kazumi with his DNA from his Evol Trigger in order to retrieve the last Lost Bottle. He has Kazumi get up, shock Misora and Sawa, before bringing him the CD Lost Bottle and Evol-Trigger. After transforming into Black Hole Evol, Evol places the final Lost Bottle in the Black Pandora Panel and absorbs it to achieve his true form.

After easily defeating Kamen Riders Cross-Z Magma, Grease and Rogue, as well as demolishing several buildings in the process, Evolt grabs Sento and warps the two of them to an unnamed planet. where he announces his intention to destroy every planet in the universe. He then creates a massive Black Hole and uses it to annihilate the planet and all of its inhabitants, leaving him and Sento stranded out in space before he warps them both back to Earth.

However, Sento realizes that the Genius Bottle is powered by hope and not anger, and uses that to use it to transform into Kamen Rider Build Genius Form. Build Genius Form, Cross-Z Magma, Grease and Rogue then all Rider Kick Evolt at the same time in order to force the Black Pandora Panel out of him. Evolt grabs the Black Pandora Panel before the heroes can claim it, but Sento punches him with the Hazard Trigger, knocking him out of his complete form and purifying two of Lost Bottles as well as knocking them out of the Black Pandora Panel. Evol attempts to grab the two Lost Bottles, but Cross-Z Magma snatches them up. Evol then opts to retreat rather than stay around any longer.

Back at the tower, Evol watches a news report announcing the governors for the three regions (who are all secretly members of the Blood Tribe). Utsumi then walks in and accuses Evol of not being interested in ruling Japan at all and instead wanting to buy time in order to complete the Black Pandora Panel. Evol responds by grabbing Utsumi by the throat and threatening him to not reveal his true plans to the Kamen Riders.

Kamen Rider Build: Be The One
Evolt appears as the overarching antagonist of the movie Kamen Rider Build: Be The One. He met with the three new governors of the regions of Japan who are really, along with himself, the last surviving members of the planet-devouring extraterrestrial clan known as the Blood Tribe possessing the other members of the Mars expedition: Kengo Ino, Ryoka Saiga and Mitsuomi Gohara, as well as the ones responsible for manipulating the three regions of Japan into waging war with one another. The three state they intend to finish what Evolt started and consume the planet, to which Evolt tells them that he will not interfere with what they do, but reminds them that he has the upper hand with the power of the Pandora Box.

At the end of the movie, after his fellow Blood Tribe members have been defeated by the Kamen Riders, Evolt shows up to collect their Lost Bottles.

Challenge to the Kamen Riders
Following the events of Kamen Rider Build: Be The One, Evolt makes an announcement to the entirety Japan where he reveals himself as a being of extraterrestrial origin and declares his intentions to destroy the world. He goes on to challenge the Kamen Riders to a final battle to decide the fate of the planet and tells them to meet him at the summit of the Pandora Tower and to bring the Lost Bottles.

In preparation for the battle, Evol practiced fighting a simulation of a Strong Smash Hazard and a Stretch Smash Hazard, easily destroying both with only a single strike. He then remarks to Utsumi that he's making a good replacement for Shinobu.

On the day of the final battle, a crowd of people, including news reporters, has gathered around the Pandora Tower in order to witness the fight. To get them to back away from the Tower, Evolt flings a helicopter near them. Sento, Ryuga, Kazumi and Gentoku then arrive right before Evolt makes his entrance, accompanied by a squad of Hard Guardians. Evolt proceeds to explain to the four the rules: they will have to make it to the top of the tower, and for every ten minutes that they aren't up there, he will destroy a section of Japan with one of his black holes. Evolt then teleports off to the top of the tower and leaves his Hard Guardian army to fight the Riders. Transforming into their Kamen Rider forms, the four combine their attacks to destroy the entire army, before smashing a hole in the Tower and making their way inside.

At the top of the tower, Evolt decides to make things interesting and, reverting to his Evol Cobra form, sends off a fraction of his DNA to assume the forms of the Hokuto Three Crows in order to mess with Kazumi. Upon seeing the three alive once again, Kazumi instantly identifies them as fakes. Complimenting that he's impressed he caught on, Evolt tells the Riders to keep moving before he destroys another section of Japan. Telling the other Riders to go along without him, Grease stays behind to take on the mimics of the Hokuto Three Crows.

While fighting some regular Guardians and Hard Guardians, the other Riders briefly contemplate going back to help Grease, right before Evolt destroys another section of Japan, causing them to realize they have to move on.

After Kazumi transforms into Kamen Rider Grease Blizzard using the second Build Driver recovered from Shinobu Katsuragi, Evolt watched from atop the Pandora Tower, remarking that he "had gotten all dressed up to die." Evolt later sent out clones of Remocon Bro's and Engine Bro's to challenge the Riders. Kamen Rider Rogue opts to stay behind to fight them, telling Build and Cross-Z Magma to go on ahead. Initially being overpowered by both of them, Rogue soon receives assistance when Mad Rogue shows up and reveals he was working against Evolt the entire time. The two then fight the clones, who merge together to form clone Hell Bro's. They manage to finish the clone off by combining their powers, destroying it and causing it to drop the Hammer Lost Bottle.

Evol Cobra himself then shows up to claim the Lost Bottle and attacks the two Riders. Mad Rogue then reveals he is able to use Evolt's phases thanks to him collecting some of Evolt's DNA and fights the evil Rider one-on-one, only to be defeated and have his transformation canceled thanks to his body shortening out. Evolt then reveals to Gentoku and Sawa, who had showed up to deliver the Pandora Box panels, that Utsumi had to be turned into a cyborg after Gentoku shot him off a cliff due to him being heavily injured. In a rage, Rogue attacks Evol Cobra, only to be overpowered and knocked out of his transformation. Evol then attempts to finish them off with the Steam Blade, but before he can strike them Utsumi gets up to block the attack, dying to protect the Lost Bottle. Gentoku then uses the chance to teleport himself and Sawa away.

Meanwhile, Kamen Rider Grease overpowers and beats down Evolt's clones of the Hokuto Three Crows, managing to destroy all three of them. However, using the Blizzard Knuckle to transform causes Kazumi to begin to die. Not being able to prevent his demise, Kazumi uses this as an opportunity to purify the Castle Lost Bottle for Sento, which he hands to Misora as he dies in her arms.

As Evolt annihilates another section of Japan with a black hole, the remaining Riders and Sawa reach the top of the Pandora Tower and begin treating their wounds. Misora then shows up to deliver the news the Kazumi is dead. As the five all grieve, Evolt shows up to confront them. Looking straight at him, Sento screams "Evolt!"

Battle Atop the Pandora Tower
After mocking Sento and co. for their humanity, Evolt transforms into Kamen Rider Evol Black Hole and does battle with the three remaining Kamen Riders, Build, Cross-Z Magma and Rogue. Evol easily manages to overpower the three Riders and obtain the two Lost Bottles he needed to become his final form. After transforming into his monster form, Evol beats down the three Riders again and knocks Sento and Ryuga out of their transformations. He then creates a massive black hole over the Earth and uses it to begin consuming the Earth, destroying the Moon in the process and allowing Evolt to assume his ultimate form. However, Evolt opts to drag out the destruction of Earth for a bit so he can witness the despair on Sento and Ryuga's faces for a bit longer.

Despite his injuries, Rogue refused to go down and charged at Evolt to attack him all by himself. Despite Rogue's best efforts, he was unable to do any damage against Evolt and was overwhelmed by the alien's power, having part of his faceplate shattered in the process. Thus, Gentoku instead opted to go for the Evol Trigger, the source of Evolt's power. He succeeds in damaging it, but Evolt fatally injures him soon after and knocks him out of his transformation, causing him to die and fade away.

Inspired on by Rogue's courage and the cheers of the people at the surface of the Pandora Tower, Sento and Ryuga got up and transformed into Kamen Rider Build Genius Form and Cross-Z Magma in spite of their injuries to take on Evolt. Evolt attempted to fight them, but the damage done to the Evol Trigger by Gentoku caused him to become paralyzed, granting Build an opportunity to attack him. Using the Genius Finish, Build manages to force the Black Pandora Panel out of Evolt, which Ryuga then grabs and combines with the White Pandora Panel, causing the black panel to be destroyed. Misora then rushes out to give the Riders the other Pandora Panels so Build can combine the White Pandora Panel with then. Placing the White Pandora Panel with the other panels, Build begins merging their Earth with an alternate universe Earth that has no Skywall.

To complete the merger of worlds, Build attempts to use Evolt's energy to power it, but Cross-Z Magma steps in and cancels Build's transformation to do it instead, as he has Evolt's DNA. Grabbing Evolt, Cross-Z Magma flies into space with him and into a dimensional rift between the two worlds, granting the fusion enough power for it to finish.

Final Battle
However, Sento flies into the rift after Ryuga in order to rescue him. He finds Ryuga lying on the ground, though it turns out to really be Evolt in disguise. Evolt then reveals that since he has survived, the merger will cause the two worlds to collide and destroy each other unless he can be defeated. Transforming into Build RabbitRabbit, Sento fights Evolt in his ultimate form and is quickly overwhelmed and knocked out of his transformation. Assuming the form of Soichi Isurugi, Evolt mocks Sento and tells him he is nothing more than a "sham hero" he created. Sento responds by rejecting this, claiming that Build was created and built up by his friends. Evolt then reverts back to his ultimate form and prepares to finish Sento off, but is stopped by Ryuga resisting him from the inside. Ryuga gives Sento some words of encouragement, telling him that his friends all believe in him, before Evolt fully consumes him and spits out the Dragon Fullbottle.

Sento then transforms into Build RabbitRabbit and fights Evolt again. As the two battle, both begin to fade, causing Evolt to question which one of them will die first. Sento later switches to Build TankTank after being overpowered as Build RabbitRabbit, and later again to Build Sparkling form. Though he is eventually knocked out of that form and back to his base form as Build RabbitTank, Build refuses to give up and even manages to injure Evolt and knock him out of his ultimate form. Build then uses the Rabbit and Dragon Fullbottles to transform into Build RabbitDragon and uses his finishing move on Evolt. Though Evolt does his best to fend off Evolt, he is ultimately overpowered and destroyed with his energy being used to complete the fusion of the two worlds, thus creating a world where he never existed and where the Skywall Disaster never happened. With that, Evolt's reign of terror was brought to a definitive and permanent end.

Personality
Blood Stalk displays a disturbingly flippant demeanor, casually carrying out his duties as a Faust strategist and enforcer even when they involve committing atrocities. He generally acts more friendly when compared to Night Rogue, though he is just as sinister and ruthless as his ally, if not more so, turning a child into the Ice Smash just to show off his Steam Blade's ability to create Smash. He is also incredibly manipulative, and willing to play both his allies and enemies alike to achieve his goals.

Blood Stalk's cruel and sociopathic traits becomes much more highlighted as the series progresses, with him eventually being revealed to be Evolt, the entity that annihilated life on Mars. He becomes much more wrathful as Vernage and Sento continue to impede his plans, choosing to keep Sento around rather than erase his personality after he possesses him just so he can witness him harming his friends. Evolt also often allows his bloodlust and sadism to get the better of him, choosing to put off destroying Earth in order to have a "final battle" with the Riders and to screw with them some more.

He also shows an apparent disdain for technology and innovation, claiming to Sento that science causes society becoming complacent and ultimately leads to war, though this may just be him trying to screw with Sento, as Evolt is shown advancing technology for his own purposes many times throughout the series.

Episodes
"Jouketsu!"

- Blood Stalk's transformation catchphrase.

"Ciao!"

- Blood Stalk's farewell catchphrase.

"That's why humans are so interesting! So I decide not to destroy this planet!"

- Evolt laughing after Utsumi went insane and swore his fealty to him.

"I'm going to consume as many planets as I can until I'm all that's left in the universe. And that...will be the new world!"

- Evolt taunting Build before destroying a planet in episode 45.

"It's been ten years since the Skywall tragedy. Our country was split in three, Touto, Seito and Hokuto and chaos ensued. Soon, the Kamen Rider military weapons were deployed, and war broke out. As the war reached a frenzied peak, Hokuto and Touto were occupied by Seito, and a new country was born. And now, the day has finally come. As of today, our country is done! My name is Evolt. I'm an extraterrestrial being that assimilates planets to turn them into my energy! Your planet will be destroyed as it becomes a part of me! That said, I have lived here for ten years, so I've got a bit of affection for the place. For that, you get a special chance. This part is for the Kamen Riders out there! Tomorrow morning, come to Pandora's Tower and bring the Lost Bottles. Why don't we have a final battle, with the planet on the line?!"

- Evolt announcing his true identity to the population of Japan at the beginning of episode 46.

"Let me explain the rules. You boys will be aiming for the top of Pandora's Tower. But every ten minutes, I'm going to destroy a section of this country. A bit like this... The sooner you climb the tower, the more people you'll save."

- Evolt explains the rules of his challenge to the Riders.

Recap
"Ryuga: Hey... "Kiryu Sento" is what the cafe owner named you, right? Soichi: Yep! "Sen" as the character for tank, and "To," as in rabbit. Sento: You just named me Rabbit Tank! Ryuga: Then, how about "Kiryu" then? Soichi: I was on the way to my barber Kiryu when I found him. Sento: THAT'S the reason?! Soichi: Let's just start episode 9 already."

- Soichi/Blood Stalk in the recap for episode 9.

"Blood Stalk: A war's erupted between Touto and Hokuto over the immense energy within Pandora's Box! Kamen Rider Build, Sento Kiryu, loses his will to fight after destroying one of Hokuto's Smash, but to protect Touto, he will fight Hokuto's Kamen Rider Grease in a proxy battle! Ryuga: What are you doing the intro for? Blood Stalk: My voice is great, right? I always get the job done in that regard! Ryuga: Don't call it a job! Blood Stalk: Now, what'll happen on Episode 22?"

- Blood Stalk provides the intro for episode 22.

"Evolt/Sento: Pandora's Box, which contains incredible energy, has finally been opened by the extraterrestrial entity, Evolt. Kamen Rider Build aka Sento Kiryu fights against Evolt in order to rescue Banjou, whose body has been absorbed, but ends up being possessed instead. Ryuga: Hey, are you really Sento? Or Evolt? Evolt/Sento: I’m obviously Sento. Ryuga: Then make some coffee for me! Evolt/Sento: Here you go. Ryuga: Yuck! You’re really Evolt, aren’t you?! Evolt: Oh well, you got me there. Here’s Episode 37 for you."

- Evolt provides the recap for episode 37.

Trivia

 * Initially, the true identity of Blood Stalk was hinted to be Takumi Katsuragi before it was revealed to be Soichi Isurugi, and later Evolt.
 * Evol is the second snake/cobra-themed Kamen Rider since Kamen Rider Ouja.
 * Stalk provides the recap for episodes 22 and 37, and also participates in the recap for episode 9.
 * Evolt has many similarities with traditional depictions of the Devil, being a manipulator who makes deals offering power to others only to eventually screw them over. Adding onto this, he has a cobra-theme as Blood Stalk and Kamen Rider Evol Cobra, similar to how the Devil appears as a serpent in the story of Adam and Eve.
 * Evolt is similar to General Xaviax from Kamen Rider: Dragon Knight. Both are extraterrestrial beings who masterminded the events of their respective series, destroyed a planet, manipulated the Riders (and even the main protagonist's father) to further his goals. They also have the ability to assume human disguises and ability to possess a human host. Both of them have the ability to transform into Riders - Evol (Mad Rogue included) and Wrath, respectively as well as a monster form.
 * Evolt has a habit of saying "Ciao" as his farewell phrase, though he is not the only villain to do this.