Biish was the leader of the Longtooth gang in Malleon's Gate, Sharn. He's been in the game for a while now, and has a long history with Natrac. This long rivalry culminated in Biish and his gang running Natrac out of Sharn, and Natrac setting off an explosive in Biish's hideout.
He was hired by Vennet d'Lyrandar to kidnap kalashtar from Overlook.