It's completely unthinkable for Fenrir to join forces with anyone seeing as he's a lone wolf howling under the moonlit night. If enemies appear, Fenrir will annihilate them with his own hands. It would be absurd to cooperate with such a wild being.
In Norse mythology, Fenrir (Old Norse: "fen-dweller"), Fenrisúlfr (Old Norse: "Fenris wolf"), Hróðvitnir (Old Norse: "fame-wolf"), or Vánagandr (Old Norse: "the monster of the river Ván") is a monstrous wolf. Fenrir is attested in the Poetic Edda, compiled in the 13th century from earlier traditional sources, and the Prose Edda and Heimskringla, written in the 13th century by Snorri Sturluson. In both the Poetic Edda and Prose Edda, Fenrir is the father of the wolves Sköll and Hati Hróðvitnisson, is a son of Loki, and is foretold to kill the god Odin during the events of Ragnarök, but will in turn be killed by Odin's son Víðarr.
- See Raging Fenrir