Bill Cipher

"Ho ho! Looks like Mr. Brainiac finally got smart! Let's just say that when that portal finishes charging up, your dimension is gonna learn how to PARTY!! (to his monsters) Right, guys? (the monsters laugh)"

- Bill revealing his true nature and plan to Ford Pines "At last, at long, long last! The gateway between worlds has opened! The event one billion years prophesied has come to pass! The day has come, THE WORLD IS FINALLY MINE!!!!"

- Bill after successfully crossing into the real world

Bill Cipher is the main antagonist of the Disney XD series Gravity Falls. He is a very powerful dream demon who means to bring about the end of the world by opening a rift between his Nightmare Realm and the real world.

Appearance
Bill appears as a floating, yellow triangle with a single cartoon eye in the center (though sometimes near the upper corner), a black bowtie and top hat, and thin black limbs. He is sometimes seen holding a yellow or black cane as well. Bill's body also flashes when he speaks, as he has no mouth. When angered however, his color is inverted, with his eye turning black, outline turning white and yellow turning a glowing red, although his form can change to that which is desired at will. A tapestry hanging from the wall in Northwest Mansion Mystery depicts him as black or ash grey instead of yellow and with a red eye. In The Last Mabelcorn he appears for a few moments as black with a yellow eye.

While possessing a person, that person's body will take on a pale tone to their skin, and their eyes will appear yellow with black slits, similar to his own.

If needed, Bill's yellow main portion or his eye can show images like a screen.

Personality
Bill at first seems to be affable and polite, albeit obnoxious, but this easily changes within minutes of his debut, especially when he reveals his true nature: that of a highly intelligent, manipulative, murderous, and evil psychopath. He usually speaks with a high-pitched voice with a synthetized effect, but when furious or expressive, it becomes deep, guttural and satanic, similar to traditional demon depictions.

As revealed partially in his first major appearance when he pulls the teeth out of a deer, he is highly sadistic, stating that "Pain is hilarious!" He also enjoys hurting himself, as he tortures Dipper's body while possessing it, and has no problem killing or hurting children like Dipper and Mabel. An expert manipulator and master liar, he is clearly capable of fooling others into trusting him long enough for him to betray them in a heartbeat, and is falsely affable enough to influence others into playing pawns or making deals with him (which he will almost always double cross to his advantage). However, while an easily angered madman he is also highly intelligent and decisive, knowing when to pull out of a fight. As of The Last Mabelcorn, Bill is shown to be far more than simply a sadistic psychopath; he is calculating, malevolent, and diabolical, easily becoming one of the most fearsome and powerful Disney villains thus far.

However, in his final moments, Bill is shown to be very cowardly when being exploited by his own weakness, as shown when he is trapped into Stanley's mind and attempts to goad Stan to get him out, only for Stan to punch him out and erase him from existence for good.

Biography
In the episode "Weirdmageddon: Part I", Bill reveals he's been trapped in a decaying dimension, "waiting for a new universe" to call his own, for 1 trillion years. Ford Pines, Bill's main enemy, stated in an earlier episode that he's older than the Milky Way (which is 13.2 billion years old). Assuming that he's old enough to have recalled 1 trillion years of mental torment, this would mean he's older than our dimension by at least 987 billion years. In that same episode, he also referred to the populace of Gravity Falls as "single lifespanned", meaning he may have had numerous lifespans, and he may have either lived through those 1 trillion years in different lifespans, or he may have had lifespans before his time in the dimension. Other than his possible age, his "early life" (if whatever he is even has a definitive "life"), is completely unknown.

Before his debut in the episode Dreamscaperers, Bill Cipher made a cameo in the background of numerous episodes as drawings on the walls, card backings, and even in a single frame of the opening sequence, and being alluded to by series creator Alex Hirsch for the length of the season, before finally debuting in the penultimate episode.

In that episode, the season's main antagonist, Li'l Gideon, summoned him using a ritual found in Journal #2 to have him steal the combination to his safe via invading his mind. Bill made a deal with Gideon, saying that if he found the memory containing the combination Gideon would help him with his plans, probably by Bill possessing his body. Later on, after the protagonists found their own way into Stan’s mind with Journal #3, they met Bill where he warned them to keep out of it, and showed his strength by blasting a hole in Dipper’s chest, sending Mabel a few seconds into the future, and blinking two character’s she was thinking about into existence before flying into the shack in Stan’s mind. The trio followed him to try and find the memory before he could, and when they did Soos offered to destroy it with his strength, but revealed he was actually Bill in disguise, who took the memory to read it to Gideon.

However, Mabel and Soos caught up with him while Dipper looked for a personal memory, being able to knock the memory into the Bottomless Pit from the episode of the same name through one of Stan’s other memories. Seeing this, Gideon called off the deal and switched to “Plan B”, which enraged Bill to the point of growing into his ‘angry form’ and surrounding the room in flames, cornering the protagonists atop a giant stone Stan, where he tortured them by making them experience their worst nightmares. After killing Mabel’s two dream characters and threatening to do the same to Mabel and Soos, Dipper arrived just in time, having been taught by Stan in the personal memory that they can do whatever they can think in the Mindscape, and used this to fight and overpower Bill.

Before they could defeat him though, Bill teleported them all to a blank white space yelling “Enough!”, proving he was still far more powerful. But instead of killing them he stated he was impressed by them, letting them live since they might be useful later, but gave them a warning that a darkness was approaching and that everything they cared about would change. He promptly teleported away, saying he’d be watching them until then.

Bill later returned in the Season 2 episode Sock Opera, where he offered to help Dipper find the password to The Author’s laptop, in return for a ‘favor’. Dipper denied his offer and Bill disappeared, telling him he’d be back when he was ready to change his mind. He later reappeared when Dipper failed too many times to guess the password, forcing the computer to erase all its data after a countdown. During the countdown, Bill reappeared, stating Dipper looked desperate and reprised his offer, taking advantage of Dipper’s desperation, telling him he only wanted a puppet. Dipper tried to resist, saying the puppets were for Mabel’s sock puppet play, but Bill was able to convince him by asking him what she had done for him lately, reminding Dipper of how much he’s sacrificed for her without her doing anything in return.

Dipper finally agreed to the deal, only for Bill to remove his soul from his body and possess it, making Dipper the ‘puppet’. He then smashed the laptop and proceeded to express his joy and ‘test’ his new body by slapping it in the face. Upon being asked why he had broken his word, Bill revealed that Dipper was getting too close to major secrets and that he didn’t need the boy getting in his way, and left to destroy Journal #3 to stop him for good. After Mabel unknowingly told ‘Bipper’ she was using the journal as a prop in her play, he convinced her to let him play a part in it in order to get closer to the book. Dipper followed him there though and was able to tell Mabel what happened, and she went to get the book.

However she was confronted by Bipper, who threatened to drop Mabel from the catwalk and ruin her play if she didn’t hand over the journal. Mabel almost gives him the journal and he asks her who sacrifice everything they’ve worked towards for their sibling. Mabel responded by telling him Dipper sacrificed for her, and returns it by throwing the play. On the stage Mable and Bipper fight, with Bipper easily overpowering her, however she exploits Dippers body’s weaknesses, such as the fact that he hadn’t slept in more than 50 or so hours and is able to defeat him. With the body exhausted to the point of unconsciousness, Bill is thrown out and Dipper takes his body back. The twins share a moment, but Bill possesses one of the sock puppets though, telling them they can’t stop him, and Mabel sets off the fireworks used in her play, destroying the puppet and forcing him once more into retreat.

Bill appeared a third time for a short cameo at the end of Northwest Mansion Mystery. After Old Man McGucket had fixed the laptop and warned Dipper that the end of the world was coming and that they had to stop it, panning off to a tapestry with a black and red Bill on it gazing over a burning landscape, alluding that Bill was what was to cause the apocalypse.

While not specifically present, Bill was clearly referenced numerous times in the episode A Tale of Two Stans, first when a younger McGucket spoke the ominous phrase "When gravity falls and earth becomes sky, beware the beast with just one eye", and again when Ford, Stan's brother, inspected his shape out of suspicion of him being possessed by Bill, notably by checking the give away eye shape with a flashlight.

He then made another direct, though off-screen appearance at the end of the episode The Stanchurian Candidate, when Gideon attempted re-summoning him from his prison cell to strike another deal, possibly to destroy the pines family in exchange for a host to possess in Gideon.

Bill finally made his third appearance in the episode The Last Mabelcorn, where he came to Ford in a dream, establishing their past relationship and warning Stanford that he was coming. In response, Stanford had Mabel retrieve Unicorn Hair in order to cast a spell that would protect the Mystery Shack from Bill Cipher. In the mean time, Stanford showed Dipper a machine that would scan their thoughts and shield their minds from the demon as a last resort in case Mabel failed. Curious of Ford's thoughts and his history with Bill, Dipper attached the machine to Ford in his sleep and saw that he was dreaming of Bill and Ford making a deal. In his horror Dipper also knocked over the curtains on the walls, revealing the room to have once been a shrine to Bill as many paintings oh him hang from the walls and statues of him stand in the corners. Because of this Dipper believes Ford to be possessed by Bill, or worse, in league with him, to the point of almost using the Memory Eraser on him. Ford proves he's still on their side though, and reveals his history with Bill. Apparently, Stanford hit a roadblock in his research of Gravity Falls, but found writing in a cave depicting a being of knowledge that could help him, and summoned him. Bill first appeared to Stanford in a dream, where he seemed to be Affable and Friendly, offering a game of chess and Dream Tea. Bill lied to Ford, telling him he was a Muse that chose a brilliant mind to inspire every century. In his flattery Ford made a deal with Bill, that in exchange for total access to Ford's mind Bill would help Ford by telling him to build the portal. But when McGucket was sucked into the portal, Bill's true plans were revealed and the triangle exposed as a malevolent, psychotic monster. It is learned he was going to use the portal to open a gateway between the Nightmare Realm he exists in and the physical world, allowing him to achieve physical form and unleash his fellow demons, in his own words "teach this dimension how to party". It is also revealed that Bill is older than "anything in our universe", and that Bill had been manipulating history by making deals with people throughout time, apparently for the sole purpose of one day creating the portal. Ford tells Dipper this is why they must protect the Dimensional Rift, and that if they worked together they could be the last people to be tricked by Bill. After the spell is successful, Ford tells Dipper that anyone inside the bubble surrounding the shack would be safe from Bill's influence. However, Bill is watching them from his dimension, and decides that if he can't effect anyone in the Mystery Shack, he would have to look for his next pawn on the outside as a series of images of the rest of the cast flash over his eye.

Bill next appeared in Dipper and Mabel VS The Future, where he possessed Blendin Blandin in order to have a vessel to destroy the rift. Using Blendin, he convinced Mabel to steal the rift for him by promising her that he can extend summer for her with it for as long as she wanted. As it turns out, the rift is in Dipper's backpack (which Mabel took by accident). Upon receiving the rift from Mabel, Bill promptly smashes it on the ground, opening the gateway to the nightmare realm. Leaving Blendin's body, the episode ends with Bill laughing triumphantly at Ford and Dipper as he makes his entrance into the world and ignites "Weirdmageddon".

In Weirdmageddon - Part 1, Bill finally attains a physical form and frees his gang from his dimension. He then wreaks havoc on the town of Gravity Falls and turns it into an apocalyptic, nonsensical wasteland while declaring that he intends to do this to the entire universe. Dipper and Ford then enact a plan to take out Bill with a quantum destabilizer, but fail due to the abnormal environment. After being captured by Bill, Ford is offered the chance to join him, but is turned into a golden backscratcher by the demon after refusing. After easily defeating Dipper, Bill sicks his henchmen, 8-Ball and Teeth, on the boy to eat him and flies up to his new, floating castle to party with his crew. After three days of non-stop partying, Bill is confronted by Time Baby and his police force, who came to arrest him for both using the body of Blendin Blandin for his scheme and to stop his plot to alter reality. Bill, however, is unfazed and promptly kills Time Baby and his police by disintegrating them.

Meanwhile, Dipper, after escaping from 8-Ball and Teeth, is on the search for his sister, Mabel, who Bill imprisoned in order to honor his deal with Gideon (who he also broke out of jail). After a confrontation with Dipper and Wendy, Gideon calls upon Bill's minions to take them and Soos to the dungeon in Bill's castle. After being convinced by Dipper that Mabel will never love him and that he can't force her to, a newly reformed Gideon decides to help aid in his former enemy's cause by giving him the key to Mabel's imprisonment bubble. He and his prison goons then leave to confront Bill and his minions.

In Weirdmageddon 2: Escape From Reality, Bill taps a fork on Golden Ford to grab the partying monsters' attention, and announces that they will now unleash their chaos on the whole world. As all other monsters take to the skies to spread destruction, they slam into an invisible forcefield without warning, Bill exclaiming, "WHAT?!" He figures out that their chaos has formed a barrier around Gravity Falls, the only area they can currently reside in, meaning that they can't spread their destruction throughout the world. Upon learning of this, Bill realizes that this might be more difficult that he thought. One monster complains that they broke something, and Bill angrily retorts, "WALK IT OFF!"

He considers getting Ford 'out of retirement', believing that the latter may have the answer to breaking down the barrier. He then finds out from Keyhole that Gideon let Dipper, Wendy, and Soos into Mabel's bubble. Bill simply laughs, explaining how the bubble is his most diabolical trap of all. He tells Keyhole to fetch Gideon and have the day off while Bill prepares to expand his world upon Earth, and later, the universe.

In "Weirdmageddon 3: Take Back the Falls", Bill releases Ford from his frozen prison to gain knowledge about the forcefield that's keeping him in Gravity Falls. Bill establishes that he comes from a flat dimension where he is implied to have committed mass genocide against his own kind, including his family hinted back in the 2015 Bill Cipher AMA on Reddit. Ford refuses to cooperate with him, which instantly tests Bill's patience. Bill starts torturing Ford in order to get the answer to his dilemma. As soon as the Pines family and their resistance group made a giant robot to fight their way to the Fearamid, Bill goes after the Pines and petrifies Ford before he could try to stop him. Bill orders his henchmaniacs to fight the resistance. When that fails, as the townspeople worked together to take down most of the henchmaniacs, Bill takes matters into his own hands and tries to destroy the robot, but with no success, due to the Mystery Shack being protected by unicorn hair that Dipper and Ford enforced back in The Last Mabelcorn. The robot tears out Bill's eye, where he complains to the resistance on how long it will take for it to regenerate. Unfortunately, as soon as Bill regenerates a new eye, he instantly finds the robot's weak spot and uses it to take down the robot easily.

The Pines family unites with some of the other townspeople in order to learn about Bill's weakness. They learn about the Bill Cipher Wheel and tried to use in order to defeat Bill for good, but it fails, as Stan refuses to hold hands with Ford due to bearing a grudge and holding some resentment for his twin brother over the whole portal incident. Bill immediately retaliates by transforming Soos, Wendy, McGucket, Pacifica, Robbie, and Gideon into tapestries in his lair. Dipper and Mabel risk their lives by angering Bill with their pranks in order to distract him, while Stan and Ford try to figure an alternative solution.

Death
"You're making a mistake!! I'll give you anything: money, fame, riches, infinite power, your own galaxy, PLEASE!! (starts to glitch) NO!! What's HAPPENING TO ME?!!! (saying a message backwards as he glitches) STANLEY!!! (gets punched on the face by Stan) AAAAAAAAH!!!!!"

- Bill's last words before he is destroyed by Stanley

When Bill finally captures Dipper and Mabel and ponders on who to kill first, Ford reluctantly surrenders and orders Bill to let the twins and his brother go in exchange for access to his mindscape. Bill gladly accepts and instantly leaves his physical form to enter Ford's mind. However, it turns out Ford and Stan planned a switcheroo and Bill ends up in Stan's mind, where Stan taunts him for falling for the trick. Ford, with no other option, reluctantly uses the Blind Eye Society's mind-erasing weapon to wipe out the memories of his twin brother in order to defeat Bill for good. Realizing that he's been tricked, Bill angrily calls off the deal, but he gets locked within Stan's mind as the dreamscape and living room of the Mystery Shack burn in flames thanks to the mind-erasing weapon. Bill cowardly pleads for mercy by appealing to Stan's greedy nature with riches and power, but Stan selflessly refuses, as Bill has harmed his family too much to deserve any mercy. As Bill begins to glitch, he cries out Stanley's name and angrily charges at him, but Stan retaliates by punching Bill in one single blow, obliterating the maniacal triangle demon to his death in pieces right before his memories are wiped out.

With Bill finally erased from existence, Weirdmageddon has ended, and all of the monsters were returned to their dimension and the rift is finally sealed off for good, turning all of Gravity Falls back to the way before Weirdmageddon has started. As Stan manages to regain his memories (thanks to the help from the Pines family), the only trace of Bill left is his physical form now in stone, that can be seen at the end of the climax, as well as the end of the final episode's credits.

Trivia

 * His name could be a reference to the Beale ciphers, encrypted manuscripts which are said to lead to a great, hidden treasure and which only one of three have been decoded.
 * This is entirely possible as codes and ciphers are hidden all throughout the series.
 * Bill can be summoned if one were to recite an incantation found in Journal 2.
 * He may have been possibly based on The Eye of Providence.
 * Bill is voiced by series creator Alex Hirsch, who also voiced Grunkle Stan, Old Man McGucket, and many others.
 * Bill is considered to be among the most evil Disney villains, comparing to the likes of even Scar and Judge Claude Frollo. He has no problem killing children, is extremely sadistic to the point of torturing Dipper's possessed body, will do anything he can do to get what he wants, and considers the destruction of our universe a mere game.
 * He has some similarities to Yuuki Terumi. Both act nice as a facade and both are incredibly sadistic once their true nature is revealed.
 * Bill Cipher has a strong resemblance with Dimentio from Super Paper Mario as:
 * Both have the main goal to destroy all life; though Dimentio actually wanted to destroy all the worlds to create "perfect" new ones for him to rule while Bill just wants to bring "the end times" to everything with reasons still unknown.
 * Both are always floating the most time when they appear.
 * Both appear to have unlimited power, being considered the most powerful villains in their respective franchises.
 * Both made a deal with the protagonists to presumably give "help" to them when they most needed it and ended betraying them (Bill taking control over Dipper's body and Dimentio brainwashing Mario and Luigi to help him on his plans).
 * Both have humorous qualities, though being very ruthless on their goals and even when they are committing misdeeds.
 * Both help the main antagonists at first, but are later revealed to be the true main villains.
 * Various things were discovered about Bill Cipher during a Reddit AMA, including the possibility of him once having a family, having something to do with Gompers in the past, and his favorite music being 10 hours of Rising Shepard Tone.
 * The AMA also revealed that Bill Cipher thinks in capital letters.
 * It is never made clear what Bill truly is. While he is called a 'Demon' by the characters, creator Alex Hirsch has confirmed that this is just a name for lack of better description. Ford even states that no one knows really what he is. Because of his reality manipulating abilities and strange nature, it is highly possible that he is based on the Eldritch Abominations and Great Old Ones of Lovecraftian Lore.
 * As he is about to be erased he says something that if reversed says "A-X-O-L-O-T-L MY TIME HAS COME TO BURN, I INVOKE THE ANCIENT POWER THAT I MAY RETURN" which might mean he cast a spell that may resurrect him, though this isn't confirmed.