Percy Jackson and the Olympians: Legends

Fenris is described as larger than an average Labrador retriever, but definitely not much larger than a regular wolf which surprises Magnus. His legs are long and muscular, built for running, while his shaggy gray coat swirls with tufts of black. Fenris' eyes shine with a blue light that "sent a xylophone mallet down the back of [Magnus]' ribcage". According to Magnus Chase, Fenris' eyes are colder and more intelligent than those of any predator he'd ever encountered – animal or human. In addition, the wolf's black lips curl in "a very human sneer". Despite Fenris' gleaming white fangs and his utter hatred for the wolf, even Magnus admits that he is a handsome animal. Apparently, his fur only shines after a long bath in the blood of Asgardians.

Much like his father, Fenris is manipulative, sly, humorous, charming and very ruthless. He likes to trick those who come to his prison, trying to look harmless and contained, he lures his victims with his charm into getting closer, so he can attack and kill them. He did this to Blitzen's father. Fenrir is also very arrogant, due to the fact that he can't be killed before the Ragnarok, he claims to be invincible. His cruelty extends to the point when he sunk so low as to send wolves to kill Magnus's mother just so that Magnus could become strong enough to retrieve Sumarbrandar in order to free him. This however, proved to be his undoing, as Magnus instead used the sword to retie him, leaving him bound until Ragnarok.

Fenris is the wolf son of Loki and the jötunness Angrboda, who is destined to eat Odin during Ragnarök. He is the brother of Hel and Jormungand, as well as the half-brother of Alex Fierro and Samirah al-Abbas. He was raised by the Aesir until he quickly grew and became a threat and started to rampage across the Nine Worlds. They tried to bind him twice but he broke free both times with his immense strength. The gods then had the dwarves make an indestructible rope to bind him. When they presented Fenris with the rope he became suspicious and agreed to let them bind him only if one of the gods put their hand in his mouth. Tyr volunteered. The wolf bit off the war god's right hand and the other gods bound and muzzled him and left him on Lyngvi until Ragnarök, when he is fated to escape from his bounds.