Fenrir has grey hair, with several strings reaching down his spine. He has grey eyebrows and yellow eyes.
Before his parents were murdered, Fenrir wore a pink coat with yellow fur, blue cloth bracers and leggings, a blue belt and brown boots.
While growing up with the wolves, he wore blue pants, brown boots, blue bracers, the same belt and his coat was replaced by a tattered fur shirt.
His casual attire is replaced by a white outfit with sleeves while wearing his God Robe.
Fenrir was once a happy human being living with his parents. After witnessing them both murdered at the hands of a giant bear, and the others with them flee rather than help, Fenrir is instead being rescued by wolves. Accepting them as his new family, he gradually comes to hate humans for their own selfish needs.
Fenrir confronts Shiryu near a large, frozen waterfall in Asgard shortly after the Bronze Saints splitting up in order to defeat the God Warriors and retrieve the Odin Sapphires. Ordering his wolves to devour Shiryu, Fenrir is furious as the Dragon eliminates a large pack of the wolves, jumping down to the waterfalls himself to face the Bronze Saint. Stating his name, northern star and rank, Fenrir attacks Shiryu with his "Wolf Cruelty Claw" which Shiryu is unable to see through, inflicting several cuts on the Bronze Saint.
Unleashing the same move once again, Fenrir manages to get close to Shiryu and inflicts cuts near his eyes, making it harder for the Bronze Saint to see as blood drips down in his eyes. As Shiryu is forced to close his eyes, Fenrir and his wolf Gingu slowly approach Shiryu, and he is unable to locate Fenrir among the two.
Detecting Fenrir among the two, Shiryu unleash his "Sho Ryu Ha" but Fenrir easily dodge the attack before laughing it off as a weak blow. Attacking the Bronze Saint again, Fenrir is shocked as Shiryu manages to evade the blow before once again closing his eyes due to the blood dripping. Fenrir quickly strikes Shiryu again, causing him to slide down the waterfall. Following the Bronze Saint down, Fenrir steps in and impales Shiryu in the stomach with his wolf claws several times, causing Shiryu to vomit blood and fall down on the ground.
Leaving him to the wolves, Fenrir is infuriated as the Bronze Saint stands up and kicks away the wolves lunging at him, quickly pursuing and slashing the Dragon from behind before stepping on him. Furious for Shiryu not dying, he leaps up to the air and stomps Shiryu's head to the ice, polluting the ice with more of his blood.
He is surprised when Shiryu suddenly stand up again, determined to fight on. Asking the God Warrior why he hates humans so much, Fenrir reveals his childhood story of when he lost both his parents to a bear while out hunting. Adopted by the wolves, he embraced them as his new family and was later given the Alioth God Robe.
As the fight progresses, Fenrir unleash his "Northern Gunroken", further wounding Shiryu. As his wolves attack Shiryu and try to kill him, Fenrir spends a little moment with Gingu, stating that they will always be together. Suddenly, Athena's Cosmo covers Shiryu and the wolves stand back. Deciding that the one who wins the battle is the one who's right, Shiryu and Fenrir burn their Cosmo and attack with the "Sho Ryu Ha" and the "Wolf Cruelty Claw" respectively, with Fenrir's attack easily shattering Shiryu's, granting the Bronze Saint further wounds.
Asking Shiryu how he can even understand Fenrir's hate towards humans and they won't understand, Shiryu reveals his and the Bronze Saints' way of growing up without parents is not so different, landing a blow to the God Warriors' stomach. Attacking with his "Northern Gunroken", the ice shatters as Shiryu retaliates with his "Sho Ryu Ha". Launching dozens more blows which Shiryu easily dodges, he eventually sends the Bronze Saint to the ground with a kick that forces him to dodge.
Laughing as Shiryu's blood starts to freeze and cause further pain, he is horrified as Shiryu once more attacks with his "Sho Ryu Ha", this time aiming at the frozen waterfall behind him. As the waterfall collapses, Fenrir struggles to escape but is consumed by the massive amount of snow. By the time the avalanche has ended and Shiryu manages to surface from the snow, the wolves find Fenrir's body and Shiryu claims the Odin Sapphire before the wolves attack him and knock him unconscious.
Fenrir's Cosmo may be equal or stronger than that of the Gold Saints, as he easily dodges Shiryu's attacks. He can launch attacks at the speed of light as Shiryu is unable to see them.
Wolf Cruelty Claw: Fenrir focuses Cosmo into his right hand and unleash a large wave of lightspeed blows which cut his opponent like a wolf's claws.
Northern Gunroken: Fenrir's strongest move. He gathers a lot of Cosmo into his right hand and unleash several red energy waves resembling wolves which attack his opponent at the speed of light.
Fenrir wears the Alioth God Robe, one of the seven God Robes hidden in Asgard. The Robe resembles the northern wolf Fenrir from Norse mythology.