This list is a compilation of Harry Potter characters and places, not exhaustive since it doesn't include Fenrir, but is pretty good nevertheless and is annotated.
This list is a bit clearer to read and also doesn't include Fenrir, but has brief descriptions.
A brief description of the canonical Fenrir Greyback: he's a vicious brute that has made it his mission to convert as many as possible into werewolvery, especially children. Draco Malfoy is acquainted with him and has dropped his name with an enthusiasm like to that of releasing a rabid ferret from your grasp but is also afraid of him.
A quick description of the Fenrir that was introduced to Mordor in ATM1: Fea transported him there through a fire to help take care of a werewolf problem (she has odd logic, she'll admit) and he stuck around. He is now very closely watched by Alli (Seer) and Aimè (Hunter), but he is still a free citizen. Feel free to use him.
