Emerald Sustrai

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

- Emerald, to Mercury

Emerald Sustrai is an associate of Cinder and a partner for Mercury. She makes her first appearance at the end of Black and White in RWBY Volume 1.

Appearance
Emerald is a thin female with tan skin and dark-red eyes. Her hair is a light mint green cut with a straight fringe and bangs as well as two long locks on each side. She wears two bronze-colored rings on her middle fingers.

Originally, her attire consisted of an intricate, exotic-looking white top and olive undershirt along with white shorts decorated with what appears to be a gold coin-plated belt with four gold chains draping around her back from two of the coins and what seems to be a green loincloth.

She also wore a gold three-ring armband on her left arm and a string of gold beads near the same wrist. As of Volume 2, her outfit has changed somewhat. Her top has thinned, her undershirt is now shallow-cut, and her armband and beads seem to no longer be made from gold.

She now also wears white pants and brown chaps that end at her calves and an overlong belt, twice-wrapped, where she keeps her weapons. Her hair is also noticeably fuller and longer and her irises are wider.

Later, she is also seen wearing a more conservative dark gray outfit with a long-sleeved collared top and white armband, possibly as part of a uniform or disguise.

History
In the post-credits scene for Volume 1, Emerald and Mercury are seen accompanying Cinder to a meeting with Roman Torchwick.

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 he doesn't 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.

Some time later, Emerald is seen with Mercury and Cinder inside Beacon Academy, who bumps into a running Ruby. 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 watches Pyrrha's fight against Mercury. Later that day, in a dorm room with Cinder and Mercury, they all begin to talk about Pyrrha's semblance and fighting style.

In Dance Dance Infiltration, Emerald and Mercury are seen entering the Beacon Dance 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.

Later in the episode Breach, Emerald watches the Grimm attack the city of Vale with Cinder and Mercury; deducing that Roman must've started the invasion earlier than expected. This results in Cinder ordering her and Mercury to assist in taking out the invading Grimm. After successfully driving them off, Emerald discusses the situation with the others on a rooftop. She notes that Team RWBY has made major setbacks in their plans, and wonders if the White Fang will listen to Cinder and her team now that Roman has been apprehended by the authorities. They are suddenly interrupted by Adam Taurus, who tells them that while the White Fang won't listen to Cinder, they will listen to him.

Personality
Based only on the sneak peek of Mercury's fight with Pyrrha, which shows Emerald observing on the sidelines along with Ruby, she seems mostly aloof while exhibiting a pretense of politeness. This is shown as she mostly ignores Ruby until she looks directly at her, to which Emerald off-handedly smiles and subsequently rolls her eyes when Ruby looks away.

She appears to have a liking for reading as she lists off many book titles while questioning Tukson. She also likes the city of Vale, complimenting it for its "tall buildings and diverse culture"; indicating that she has a taste for architecture and multiculturalism in cities. She is also willing to take some initiative, along with Mercury, to accomplish missions, such as tracking down Tukson and killing him herself when Roman was taking too long to do so. However, she is still loyal to Cinder and assures her that such an incident won't happen again. She also appears to have no problem with killing people, and even jokes about Tukson's death with Mercury after killing him.

Skills and Abilities
Emerald uses a pair of firearms with jungle-green grips, each stored inside their own separate leather casings on a belt wrapped around Emerald's waist. Emerald's weapons can take the form of a pair of dual-wielded pistols, but they can also be converted into a pair of short scythes or kamas, which also have chains attached for them. It is later shown she is a master thief and adept at pickpocketing; stealing Roman's lighter to show him she's a capable thief after he mocked her. She also has impressive reflexes and was able to avoid Tukson lunging at her with his claws.

Trivia

 * Both Emerald and Mercury lacked 3D models in Volume One, and were simply shown as 2D image sprites instead.
 * 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's possible Emerald's character was inspired by the saying "diamond in the rough."
 * Sustrai (capitalized) is the Basque word for "thief" while sustrai (not capitalized) means "roots" or "undercurrent."