Fenrir Greyback

Fenrir Greyback is a werewolf and a Death Eater.

Greyback is the leader of the werewolves who are on Lord Voldemort's side. He is a particularly vicious werewolf, purposefully placing himself near potential victims at the full moon. His purpose is to create enough werewolves to overcome all wizards. Voldemort sometimes uses Greyback as a weapon to convince unwilling people to do his bidding, often threatening to let him attack their children.

Greyback was the werewolf that bit Remus Lupin, causing him to turn into a werewolf also; he also attacked Bill Weasley, though not in a transformed state.