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. He also contributed to the Death Eater cause in the Battle of Hogwarts when he attacked Bill Weasley, though not in a transformed state.

Name etymology
Fenrir is one of many permutations of Fenrisulfr, the great wolf from Norse mythology. It is said that in the time of Ragnarok, the final battle of the gods, Fenrisulfr will outgrow the bonds that imprison him and kill Odin. Like Fenrir, he is a savage beast concerned only with hunting and killing.