The character Fenrir Greyback is a direct reference to Fenris the wolf as depicted in the Nordic mythology. In that myth, Fenris bit the arm of Tyr and was prophesied to be involved in Odin's death as will be killed by Tyr's brother Vidar during Ragnarok. The novel shares the similar mythology: Bill Weasley, Ron's brother was attacked, his face scarred during the skirmish with Fenrir like as Fenrir bit Tyr's arm; like Fenrir's involvement with Odin's death, Fenrir was amongst the group who was involved in Dumbledore's murder; Deathly Hallows resolves the story. An interesting fact that was never mentioned in this movie is that Fenrir was the wolf who infected Remus Lupin.