Here's a list of some of the named criminal groups from various fan missions and campaigns of The Dark Mod, by various authors. (If you're unsure if you can feature one of these groups in your own FM or other work, always ask their original author(s) for permission.)
A gang from Bridgeport's quarter East End, who used to fight over that part of town with another local gang, the Bowley Boys.
A gang from Bridgeport's quarter East End, who used to fight over that part of town with another local gang, the Black Hounds.
A few years ago, the head of a guild Corbin used to work for was captured and executed. His two lieutenants both wanted to take over, and each had supporters among the rank and file. The gang split into two rival groups, each fighting the other over the same territory and contacts. Corbin, a high-ranking guild member by this point, was courted by both sides, but chose not to join either. Instead, he struck out on his own.
Corbin had an adversarial relationship with the gang's current leader, Sykes.
A thieves' guild.