The Fenris wolf is an off spring of Loki and Angerboda and also the brother of the Midgard Serpent. When the Fenris wolf tries to steal the apples of Idunn from a women a hunter chases the wolf off and banishes him to Varinhem. As the Fenris wolf grew older the Asgardians feared it not be safe to allow him to roam free because he grew stronger as he grew. Eventually It lead to the playing a game with him to see how easily he could snap the bonds placed over his mouth.
Every time they put it though he would break it with ease so it eventually lead to Odin talking to the dwarfs to made and enchanted line Gleipnir. They made it for the wolf but as they went to put it around the wolves neck he sensed something might be wrong so he said to them he’d have to have one of them put their hand in his mouth as a sign of trust. The point of it was so if the fetter was truly unbreakable then Fenris wolf would bite the god Tyr arm off. In the end it was unbreakable resulting in the loss of his arm and the Fenris wolf was bound to the rock of Gioll at the gates of hell. Eventually Hela freed the Fenris wolf in and attempt to cause Ragnarok but the plans where stopped by Thor.
Eventually the Fenris wolf was free again this time by his father Loki so that Fenris wolf would join Ulik and Hyrm as all of them had used their new forged weapons made by Surtur. Together Ulik and Fenris together attacked Thor and hit the Mjolnir with so much force it took off Sif’s arm in the process. Hyrm decided to join in on the battle and together the three shattered the Mjolnir. Thor later returned back to Asgard with his allies Captain America and Iron Man and together they fought Loki and his allies. During the fight Captain America saved Thor by throwing his weapon in the Fenris wolf mouth and took it out by simply kicking it in its stomach. During the second battle as Loki was blasting at Captain America and Thor used Captain Americas shield to protect them both he launched himself off the ground and fought back at Loki and Beat both him and his son Fenris wolf. He had beat Fenris wolf so bad that he could barely stand up on his own two feet where he stood and was scared off by Captain Americas phrase towards him “Ruff” which lead to Fenris wolf running away. The Fenris wolf was then sent to kill the orphan boy but was protected by Kurse who in the end lost to Fenris wolf as he smashed his hammer inside Kurse’s skull killing him.
Fenris wolf then participated in the assault in the attack of Vanaheim This time how ever Fenris was much bigger and stronger when he encountered Thor where Thor then got Fenris bound by some the chains that where wrapped around Ulik and use Fenris to knock down Durok in order to save Sif. Fenris then broke the unbreakable chain that where wrapped around him and challenged the weak Thor but was quickly struck down by Beta Ray Bill and after he had use the full power of the Storm Breaker on Fenris wolf all that was skeleton was left behind.
Fenris wolf made one more came back to life during Ragnarok to swallow Asgards Sun and Moon assisting the bringing of Ragnarok.
Sometime before Seige and the destruction of Asgard, Fenrir was rechained again. He was then approached by a team of scientists sent by AIM, willing to set him free in exchange for providing them the means to make Asgard-grade weapons.
The Fenris Wolf, made its first appearance in Marvel comics in Journey Into Mystery
#114, released in 1965, adapted into Marvel comic mythology by writer Stan Lee
and artist Jack Kirby
, inspired and based on the Norse mythological creature Fenris. His inspirations origins go further back than that to historic documents Poetic Edda and Prose Edda
Fenris Wolf was extremely strong, high up in the class 100 range, and even stronger than a being like Thor, who already was high in the range. Apparently he could increase his strength and power, as of each encounter he grew stronger in his fight with Thor. He was also very invulnerable, although he couldn’t survive a full-fledged attack from the Stormbreaker. He can also assume a virtually invulnerable wolf form, or his wolf-like humanoid form. He has very powerful teeth and claws. Lastly, he used a hammer made of Uru forged for him by Surtur.
He later struck a deal with AIM, who freed him from his imprisonment and managed to further expand his knowledge of his own abilities. Fenris Wolf learned that he could not only become stronger as he ate more people, but he could also take on the form of his latest victim -making him a literal "wolf in sheep's clothing." AIM also educated him on many of the Asgardians, like the Warriors Three, giving him extensive knowledge of their strengths and weaknesses, as well as allowing him to make use of psychological warfare in battle.