The Wererat leader of Rizzario's Rogues, with a grudge against Our Heroes
Rizzario is the leader of the Wererat criminal organization known as Rizzario’s Rogues. After some of his Rogues were killed by the Heroes as they rescued Mathus Niko and Moonflower, he and a large group of Wererats ambushed the party, only to be almost entirely destroyed when the party fought back. Though most of the Wererats were destroyed, Rizzario and one of his lieutenants escaped,swearing vengeance on the Heroes.
Physically he is a Halfling Wererat of about 4 and a half feet tall in Wererat form. His fur (and presumably hair in Halfling form) is very dark grey, bordering on black, making him extraordinarily difficult to see at night.
Picture Credit: http://brigebane.deviantart.com/gallery/?offset=72#/d2fbi5