User blog comment:B214/Question and Answers 6/@comment-201.215.165.7-20170114145212/@comment-9595671-20170116001659

If you look on Fenrir's page, you'll see the deceased symbol by both their names in his relatives section, so it's definitely both Hati and Skoll. I don't remember who did in Hati though, I'll have to re-read Volume 7 for that.

As for Ragnarok, considering the Norse pantheon's not the only one, Ragnarok was probably not that likely unless the right events started it. This is probably a representation of Odin saying the time's have changed.

I'm pretty sure the main theme of Ragnarok is you can't fight fate and the Norse pantheon believed this, so one could say in DxD, they've started to consider otherwise and Loki just doesn't agree with that.