The Defias Brotherhood is a criminal organization from Stormwind. They formed following a bounced check.
The Defias were originally led by Edwin VanCleef, who died. The organization was then succeeded by his daughter, Vanessa.

They originally started as the Stonemason’s Guild of Stormwind, with the task of rebuilding the city following the First War. Once they finished the job, they went unpaid. After clashes between authorities and the Guild, the Guild turned into the criminal Defias.

I think they’re an interesting idea but, as usual, the idea was kinda wasted by Blizzard. More to be written later.