The Rat King seemed to be some sort of alchemist who had set up a lab in the sewers of Thrushmoore. At some point his experiments went awry, destroying his labratory and a small portion of the sewers. Whatever kind of man he was before the accident, the Rat King emerged with his rodent side in full control. He had raised and trianed an army of normal sized and dire rats to inflitrate the town at night, and steal from the citzens. What his goal was in raising a treasury is a secret that died with him, as his body plunged into the murky depths of the sewers.