Straven Enroy is a professional thief and one of the leaders of the Phoenix Gang. He is found in an underground basement in Varrock, in the lair of the gang. For players who are starting the quest Shield of Arrav, Straven assigns the player the tasks of killing Jonny the beard before he will let the player become a part of the Phoenix Gang. He also provides the weapon store key to players who are members of his gang.
Straven claims to be the head of the "V.T.A.M." corporation to people who aren't a member of either gang. This is a cover for his gang, and the corporation likely doesn't exist.
Straven used to be attackable (with a combat level of 23). He attacked any player who is a member of the Black Arm Gang that talked to him. But after Varrock had its graphics updated, he became an unattackable NPC.
In the Varrock Census he is listed as a legitimate businessman, a common claim of gangsters in popular culture.
When you tell Straven that you have lost your "Master thief armband" on a Free-to-play server he will tell you that "This server isn't secure! Talk to me again on a members' server!", making him one of the few NPCs to break the fourth wall.
Straven could be a reference to the character Stragen in the Elenium and Tamuli book series by David Eddings, as Stragen was the leader of a large crime gang in a city called Emsat, and their names are spelled very similarly.
Although Straven is the only leader that appears in the Phoenix Gang base, he remarks he is one of the leaders and not the only one.