The Dark Brotherhood is a faction originally created and led by Malevolence AKA Dark Slade. Malevolence first created the DB after leaving his host's body and searched for henchmen to join his faction. The dark being found a group of human sized decepticon-like robots, now known as the Mini-Cons, who were a small street gang at the time. Malevolence took the thugs in and after a few years of training, he turned them from simple gangsters to cold, calculated, and disciplined military combatants.
The DB started their attacks in Philidelphia when they attacked Drew Cages birthday party at the old ECW Arena. Malevolence tried to drain Avatar Korra's energy but failed and the DB drove away.
Later on in the night Malevolences was killed by Slade for good. Deadpool put Malevolence in the No Escape Zone.
The following day the rest of the DB attacked Slade and Ashley Williams which turned out into a all out battle between Riot Bots and the DB. Later the DB formed together to become a huge robot which was destroyed by Goku after using the Spirit Bomb on them. The blast killed all except for Zector, Black Wind, Jack Knife, and Slicer. The DB afterwards scattered and are planning to reform at top secret coordinates.
The next night the remaning Mini-Cons ambushed Korra and Katniss Everdeen