Wikipedia
Maugrim
Maugrim is a fictional wolf, a servant of the White Witch in the book The Lion, the Witch and the Wardrobe by C. S. Lewis. He is Captain of the witch's Secret Police (though only one of his lieutenants is ever seen). In early American editions of the book, Lewis changed the name to Fenris Ulf (a wolf from Norse mythology), but when HarperCollins took over the books they took out Lewis's revisions, and the name Maugrim has been used in all editions since 1994.
Maugrim is one of the few Talking Animals who sided with the Witch during the Hundred-Year Winter. ( Nikabrik in Prince Caspian indicates that Narnian wolves have no loyalty to Aslan.)