Blog post elsewhere on Fenris
Fenrir is more controversial than even Loki in heathenry. He is seen as raw and uncompromising Destruction and I have found that some heathens take an almost Southern Baptist view of Fenrir with him being a demonic force of pure evil. I will admit that, while I see him as a very terrifying and uncompromising force of Destruction, I also see that as a necessary part of life.
The Aesir bound him to try to prevent something that in the end they almost made a self fulfilling prophecy. Fenrir also adds to the stories of Tyr and Odin in strong ways. Tyr as the honorable warrior who sacrifices for the community and Odin as the general/king/seer trying hard to control events that he can only partially effect. But, despite all of this, Destruction is always there. We can despair, or we can accept this truth and stand back up and face it in whatever way we can. That act of standing, often with the help of community, is what makes us who we are.
Here is a post by someone I correspond with regarding Fenrir.