Leader of all Bruja guilds is Sarta
History
Created during the Age of Midnight, five individuals were responsible for founding Bruja. Ramsey (Triste) originally had the idea of Bruja. Shevaun (vampire) and her long-time lover and partner Adjila (Triste) jumped on board to found Crimson. After Ramsey left, Kristoph (human) and Kral (Mistari) founded Frost and Onyx, respectively. Shevaun, Adjila, Ramsey, and Kristoph have since left Bruja and very few know that they were involved in the first place.
According to Lord Daryl, the Bruja guilds were founded in opposition to Midnight, although they are primarily mercenary guilds and can theoretically be bought for an alliance with Midnight.
Seeming to back up what Daryl said, Adjila commented that "Bruja was never allied with Midnight."
Crimson
Founded by: Shevaun and Adjila.
Current Leader: Ravyn Aniketos
Seen as the most "elite" of the guilds. Crimson is who you go to if you want a subtle kill, something covert, something untraceable. Maybe you want someone to disappear, or else you just don't want it known who done it. Crimson is the guild you go to when you need a job done, you need it done right, and you have a whole lot of money to put behind it.
If you have limits or rules (ie, "I want him dead but I don't want his daughter to see it" or "I want him dead in a way that everyone will think it's a suicide"), you want or don't want something specific, you go to Crimson.
Also, Crimson is where you go for the most intrigue. It's not always about the kill. Sometimes it's information. Crimson also has the hackers, the spies, the telepaths, etc.
Onyx
Founded by a Mistari named Kral.
Current Leader: Kral
You go to Onyx if you want flash. You go to Onyx when you want a kill and you want everyone to know it was no accident. As the phrase goes, a Crimson member can walk into a crowded room and make a kill so quietly no one sees it happen and no one knows anything is wrong until the target falls. An Onyx member will go into that same room and shoot a crossbow across it.
Beyond your basic murder, Onyx is also good for flashy setups, but they aren't who you want to go to for soft-footed quiet work or for anything you want to look like an accident.
Shapeshifters in Bruja tend to gravitate toward Onyx.
Frost
Founded by a human named Kristoph.
Current Leader: Christian Denmark (Triste).
Frost specializes in being invisible, and being deadly without weapons. Frost deals with the environment. They can be quiet or they can be loud, but they get the job done one way or another.
Frost members can be deadly assasins, but they're also the ones you go to for jobs Crimson and Onyx would consider plebian: thievery, bribery, arson; these are jobs the Frost guild handles, and handles very well.
Miscellaneous Information
Hiring: Sometimes clients will approach the leader, and the leader will recommend someone to hire, or approach one of the members himself/herself; sometimes people will just track down guild members like Jillian did. And, if you don't like the in-person route, you can use a pushpin and a piece of paper, since there's a big ol' bulletin board. I think Kral is advocating the use of online. -Ahar
Prisoners: Bruja doesn't do much of anything as a cohesive group. An individual member might for some reason keep a prisoner, but there wouldn't be a place at any of the guildhalls to do so. If there were, it would be pretty easy to just hire someone else from the guild to let them out.
As a rule, Bruja members generally don't believe in letting someone live.... enemies left alive tend to come back with grudges, after all.
