Emerald Sustrai

"Mercury, I will seriously pay you to shut up."

- Emerald to Mercury. "I don’t care about Salem! But I owe Cinder everything. You want to fight her that bad? Be my guest."

- Emerald to Ruby before creating an illusion of Salem.

Emerald Sustrai is a major antagonist in the American web cartoon series RWBY. She is one of Cinder Fall's two right-hands alongside her partner, Mercury Black.

She is voiced by Katie Newville.

Personality
Emerald initially appears to be extremely affable and disarmingly friendly; however, this belies a darker side of her character. On the whole, she seems to be genuinely outgoing, gregarious and quick-witted, if a little short-fused and impatient. She can also act a little childish and petty, such as when she stuck her tongue out at Roman Torchwick after she stole his lighter to mock him.

In "Best Day Ever", when she talks to Tukson about books, she seems to be very knowledgeable and intelligent about books and enjoys reading, as she lists off many titles. She also likes Vale, complimenting the city for its "tall buildings and diverse culture".

She also has a tendency to maintain a pretense of friendliness amongst people in order to gain their trust. This is shown on multiple occasions in "Best Day Ever", where she pretends to be extremely kind and demonstrative to the Shopkeep in order to catch him off guard and steal his wallet. Later in the same episode, she puts on a friendly act around Tukson before threatening and killing him. Another example is in "Extracurricular"; where she mostly ignores Ruby Rose until she looks directly at her, when Emerald off-handedly smiles and then rolls her eyes when Ruby looks away. In the episode "Round One", she states that she dislikes Team RWBY for their cheery and positive attitude, regardless of her acting as their friend for the time being.

Emerald also shows a strong sense of loyalty, specifically to Cinder, whom she appears to be incredibly eager to please. Accordingly, she is willing to take the initiative to impress her, such as tracking down Tukson and killing him. When Cinder rebukes her for killing Tukson, she defers to Cinder's judgment, quickly apologizing.

Judging from the composed and nonchalant way that she talked about killing Tukson, she appears to have no qualms about killing, even lightheartedly joking about it afterwards with Mercury. However, another side of her is seen in "Battle of Beacon", where she seems to be overwhelmed and disheartened at the sheer scale of the destruction and violence taking place, calling it "almost sad". Nevertheless, Emerald continues to demonstrate loyalty to Cinder, as in the "The Next Step" in which she speaks for Cinder, who has lost her voice.

According to Emerald, her loyalty is exclusive to Cinder, rather than to Salem as well, and only complies to her plans and wishes due to owing Cinder "everything". Upon learning of Cinder's apparent demise, she immediately breaks down crying and (in a fit of despair and rage) creates a nightmarish illusion of Salem visible to everyone in the room, far exceeding her normal limitations of her Semblance.

Past
Emerald lived in Mistral's city before being recruited by Cinder Fall. She lived day to day without a guarantee of enough food, always resorting to stealing to get by. Cinder saw her use her Semblance to steal a ring from a jeweler and asked her to come with her, guaranteeing a source of food. Cinder later recruited Mercury Black, and the three have traveled together since.

Volume 2
In "Best Day Ever", Emerald appears lost and runs into the shop owner of the newly reopened From Dust Till Dawn, asking for directions to a certain address. As she rounds a corner, Mercury states that he knew she was lost and she offers to pay him to be quiet using money she stole from the shop owner. They arrive at a book store owned by a Faunus named Tukson.

Emerald begins to ask if he has certain books because of his shop's catchphrase, but she eventually asks him for a book that he does not have. Things turn serious as Emerald reveals that she knows he is planning on running from the White Fang and that he knows why they are there. She asks him if he is planning to fight back and he shouts "Yes" before lunging at her. She ducks under him and Mercury kicks him as he is in the air; killing him.

Emerald and Mercury then return to Roman's base and he questions where they were all day; taking the address from Emerald's pocket without her noticing. Emerald and Mercury confirm that they were cleaning up Roman's mess. When Roman threatens them, Cinder appears and Emerald informs her that they killed Tukson; but Cinder seems more annoyed at their actions as it risks ruining her plan. Emerald then leaves with Cinder, but shows Roman that she managed to steal his lighter.

In "Welcome to Beacon", Emerald is seen with Mercury and Cinder inside Beacon Academy, posing as students from Haven Academy. She bumps into a running Ruby while walking down a hallway. Emerald helps her up, but tells her to mind where she is going. She is then redirected with Mercury and Cinder by Ruby who points them in the direction of their building as transfer students.

In "Extracurricular", Emerald is seen observing a battle between Pyrrha Nikos and Team CRDL, and later Pyrrha against Mercury. Later that day, in a dorm room with Cinder and Mercury, they all begin to talk about Pyrrha's semblance, and how skilled she is, as also listening to Cinder's plan.

In "Dance Dance Infiltration", Emerald and Mercury are seen entering the ballroom together. From here, the duo spends the evening keeping track of the attendees, watching to see if anyone could interfere with Cinder's infiltration of the Cross Continental Transmit Tower. At one point, Emerald warns Cinder that James Ironwood is leaving to check on the tower. However, Cinder is able to finish her task and return to the dance before he can see her. Emerald then lets Cinder take her place as Mercury's dance partner for the remainder of the evening.

In "Breach", Emerald assists Teams RWBY and JNPR in killing Grimm; easily slaying an Ursa using her weapons. She is later present as Adam Taurus appears by Cinder's side, explaining that the White Fang will listen to him, despite numerous losses in the caves.

Volume 3
In "Round One", at the Vytal Festival fairgrounds, Emerald steals Ruby's wallet before returning it to her. She strikes up a friendly conversation with Team RWBY, and it is revealed that she is participating in the tournament alongside Mercury, Cinder and an undercover Neopolitan.

After exchanging pleasantries with Team RWBY, she turns to Mercury and expresses her distaste for all of them, telling him she cannot stand how they always seem so cheery. However, she also shares the intel they had been sent to get: Weiss and Yang will be fighting in round two. Emerald, Mercury and Cinder are then seen spectating the match between Team JNPR and Team BRNZ.

In "It's Brawl in the Family", Emerald is later seen at Cinder's dorm room when Mercury reports Qrow Branwen's presence at Beacon. She asks Cinder if they need to change their plans, but Cinder tells them that they will stay the course. After Cinder gains access to Ironwood's Scroll, she tells Emerald and Mercury to return to their dorms.

In "Lessons Learned", Cinder engineers the next match of the Vytal Festival tournament doubles round: Emerald and Mercury against Coco Adel and Yatsuhashi Daichi of Team CFVY. Emerald and Mercury easily win the match.

In "Fall", after Mercury "loses" his match against Yang and has his leg broken by her apparently unprovoked, Emerald calls out his name and immediately rushes to his side, apparently showing concern for him. This was ultimately revealed to be an illusion created by Emerald, designed to trick Yang into attacking and one of the paramedics into thinking that Mercury's legs are real.

In "Beginning of the End", Cinder, Emerald and Neo evacuate Mercury in an Air Bus to their secret warehouse and head back to the Vytal Festival.

In "Destiny", Ruby sees Emerald in the front row of the Colosseum for the match between Pyrrha and Penny Polendina, even though Ruby was told Mercury's team all went back to Mistral the previous night.

In "PvP", Emerald uses her Semblance to make Pyrrha use her Semblance forcefully on Penny's swords. This causes the wires attached to them to wrap around Penny and split her in half, destroying her. Soon after, Emerald leaves the grandstands of Amity Colosseum.

In "Battle of Beacon", Emerald is seen on a rooftop with Cinder and Mercury, expressing a hint of remorse at the destruction caused by the chaos. Suddenly, she is interrupted by the arrival of the Grimm Dragon, as she remains on the rooftop.

Volume 4
In "The Next Step", Emerald is seen at Salem's Domain surveying its surroundings and accompanying Cinder alongside Mercury. She also acts as Cinder's voice due to the loss of her own speaking capabilities.

In "Of Runaways and Stowaways", Emerald is seen watching Cinder receive "treatment" from Salem. When a Seer enters Salem's meeting room, Emerald is disgusted and fearful of it. After Salem asks Cinder if she really killed Ozpin, Cinder signals for Emerald to help her respond, but Salem slams the table and demands Cinder say it with her own words, which makes Emerald step back.

In "No Safe Haven", Emerald watches Cinder train with Grimm. Upon completing her training, Cinder orders Emerald to create a vision of a kneeled and defeated Ruby Rose, which she mercilessly incinerates.

Volume 5
In "Rest and Resolutions", Cinder arrives at the Branwen Tribe campground with Watts, Emerald and Mercury.

In "A Perfect Storm", They tell Raven to bring Vernal as the Spring Maiden to Haven Academy to unlock its Relic's chamber. After negotiations, Emerald and the group return to a ship where they take rest.

In "The More the Merrier", Emerald accompanies Cinder as she leads the assault at Haven and later stops Ruby from helping Jaune. As they fight, Emerald reveals to Ruby that she does not care for working for Salem, but owes Cinder everything. When Ruby unleashes her powers to stop Cinder from harming Jaune, Emerald quickly knocks her out, though Cinder has been already been affected by the power.

In "Vault of the Spring Maiden", Emerald and Mercury team up against Yang, using her illusions to create multiple copies of Mercury. They quickly get the upper hand on her until Ruby wakes up and intervenes.

In "Downfall", Ruby and Yang are battling Emerald and Mercury as the Mistral authorities arrive to arrest the White Fang. Seeing an opportunity, Yang runs off to confront her mother and Cinder in the vault. Emerald tries but fails to stop Yang from going in. Emerald and Mercury chase after her, but are blocked from the vault by Weiss, who freezes the entrance.

In "Haven's Fate", Emerald, Mercury, and Hazel are cornered by Ruby Rose and her allies. Emerald declares they haven't won yet, saying that Cinder would be back any minute with the Relic of Knowledge and that she would stop them. However, everyone soon sees that only Yang leaves the vault, carrying the Relic. Now knowing of Cinder's apparent demise, she breaks down in tears, not listening to Mercury when he says they need to leave. In despair, Emerald cries out, creating an illusion visible to everyone in the room of a nightmarish apparition of Salem. Though it quickly disappears, it was enough to let them escape; an unconscious Emerald is carried by Hazel as he runs off with Mercury.

Volume 6
In "So That's How It Is", Emerald attends a meeting called by Salem, where Hazel admits that it was Cinder's fault that they lost the Battle of Haven. Salem tells them all that they must leave Cinder behind, though Emerald is just enthused to hear that she is still alive.

In "Lost", Emerald regrets leaving Cinder behind and considers that fact that she may not want to continue what she is doing without her. Mercury has to tell her that Cinder does not are about her, causing her to get angry and attack him. The two fight until Tyrian intervenes, telling them that if they do not love what they do regardless of the circumstances, they are in over their heads already. He then leaves, telling them that he and Watts have been assigned a special mission in Atlas.

In "Our Way", Emerald goes to apologize to Mercury, but finds him staring out a window, shocked. She looks to see Salem creating hybrid Beringels with wings on their backs. Hazel tells them that she is taking matters into her own hands.

RWBY: Amity Arena
Emerald appears in RWBY: Amity Arena as a playable unit. When deployed, she creates copies of friendly units on the battlefield.

Powers and Abilities
Emerald's weapons can take two main forms - primarily, they act as a pair of dual-wielded pistols, but they can also be converted into a pair of kama, the blades of which can detach and be swung from chains as kusarigama. Emerald seems to be quite adept with her weapons, demonstrating skilled swordsmanship and marksmanship, using both of her weapon forms to fend off the Grimm single-handedly in the episode "Breach". She later demonstrated the ability to ensnare opponents in her chains and reel them in, even from a great distance.

Emerald is stated by Mercury to be a master thief, and she has proven that she is adept at pickpocketing, with one victim being Roman Torchwick, stealing his lighter to show him that she was a capable thief after he mocked her. As seen in her fight with Coco Adel, her stealth abilities allow her to move silently and attack from an enemy's blind spot.

Emerald is also shown to have impressive reflexes, allowing her to avoid Tukson lunging at her and dodge Coco's rapid gunfire with ease.

Semblance
Emerald's Semblance is individual mental hallucinations - the ability to modify the sensory information in a person's head while their brain is processing it. She can make one (or more) see and hear things that aren't necessarily there. In other words, instead of generating an illusion that everyone nearby can see, she causes her target to hallucinate.

This power was pivotal in Cinder Falls's plot to rig the Vytal Festival and incite anger and distrust towards Beacon Academy. After Yang Xiao Long's victory against Mercury in the singles battle, she made Yang see a hallucination of Mercury getting up and attacking her, prompting Yang to counterattack by supposedly breaking his leg. However, in reality, Mercury had not attacked at all, making Yang's counter seem, to everybody watching, like an unprovoked attack in cold blooded spite. The resulting anger, outcry, shock and distrust from the masses of watchers stirred the Grimm wandering Mountain Glenn, as the Goliaths turned their attention to Vale.

Before this her power had been used to lead Amber into a trap to steal her maiden powers, where Emerald made Amber see a crying child on the road, prompting the maiden to lower her guard; and also in her and Mercury's fight against Coco and Yatsuhashi Daichi of Team CFVY. She used her power to hide herself and Mercury from the eyes of her opponents. After Emerald pulled Coco into the canopy section of the arena, Emerald tricked her again by making her see Yatsuhashi come up to her, seemingly victorious, only to have his knock out announced and broadcasted in the other section of the ring. Emerald then seized the opportunity to attack a bewildered Coco and knock her out as well, winning the doubles match.

Emerald's semblance was also the main reason Cinder first scouted her, having witnessed Emerald use her power to trick a jewel merchant, in order to steal one of his rings - the merchant just smiled at her, as she took the ring right before his eyes.

Her power is however shown to have its limits. Whilst she seems capable of controlling a single mind, controlling any more than that seems to tax her own head severely. After playing an illusion on two medics who came to pick up Mercury so they would not see his mechanical legs, she is shown to have a considerable headache. Manipulating multiple minds appears to have a severe affect on her mind, shown when she creates a massive illusion of Salem after the Battle of Haven, which everyone present can see. The fact that it was out of despair of Cinder's apparent death suggests that her emotional state can also affect the illusions she creates.

Quotes
"Hmm... Options are nice."

- Emerald, contemplating about Tukson's book selections.

"Spare us the thought of you procreating..."

- Emerald, to Roman Torchwick.

"I'm fine. Just watch where you're going."

- Emerald, to Ruby Rose after meeting each other for the first time.

"Just enough to make it look like she's untouchable. She doesn't broadcast her power, so it puts her opponent at a disadvantage."

- Emerald, on Pyrrha Nikos' fighting abilities.

"It appears all the dancers have partners."

- Emerald, to Cinder Fall.

"My teammates are all kind of... Introverted. Really socially awkward."

- Emerald talking about Mercury.

"Well, if Mercury and I see you down the line, don't think we'll go easy on ya."

- Emerald to Weiss Schnee and Yang Xiao Long.

"I just... how can they be so happy all the time!?"

- Emerald talking about Team RWBY.

"It's the heiress and the bimbo."

- Emerald, referring to Weiss and Yang.

"I'll try not to get blood on it."

- Emerald, after Coco compliments her outfit.

"I won't be the one bleeding."

- Emerald, to Yatsuhashi.

"Ugh, headache. One mind I can handle, but two is a stretch."

- Emerald, on the limitations of her Semblance.

"It's almost sad..."

- Emerald, apparently overwhelmed by the destruction she is witnessing.

"She wants to know... What about the girl?"

- Emerald, asking on Cinder's behalf what will happen to Ruby.

"You wanna get to them? You're going to have to get through all of us."

- Emerald, to Yang.

"It's not over! Cinder will come back, she'll have the Relic, and she'll stop all of you! She won't let us down."

- Emerald to everyone about Cinder.

Trivia

 * The name "Emerald" is a word meaning a gemstone that is most often found in green colors. It appears that Emerald's appearance also resembles that of Cleopatra, who was supposedly cursed by an emerald.
 * "Sustrai" (capitalized) is the Basque word for "thief" while "sustrai" (not capitalized) means "roots" or "undercurrent". It may also comes from the Spanish word "sustraer" which means "to steal" or "rob".
 * Emerald's emblem is a stylized depiction of a cut emerald. This emblem appears on the back of her white top.
 * In the episode "Best Day Ever", Emerald is established by her actions and Mercury's own words as a "master thief". Later, Roman refers to Emerald as a "street rat", a term used to describe the title character of Aladdin. It could suggest the basis of Emerald's character, as well as her name making allusion to the phrase "diamond in the rough", which is spoken in the Disney adaptation of the tale.
 * In the Japanese dubbed version, Emerald is voiced by Marina Inoue, who also voiced Dark Tohka.