1. What would have been a serious offense to the Vikings? Basically speaking, I've got a character who says something in Valhalla that causes everyone else in the place to try to kill him, mainly because it's an extreme insult to their culture. What sort of thing would trigger this reaction? (I'm looking for serious responses here, though I suppose I can work with something a bit off the wall and humorous.)
2. I've got Annwn, Valhalla, the Greek/Roman Underworld, Heaven, and Hell. What other mythical places (aside from the aforementioned) were locations where souls went to spend their afterlife? Websites describing such places would be appreciated as well. Please note, however, that I'm looking for mythical places real religions actually believed in.
Edit: I'd like to thank everyone who replied between the time this was posted and the day after. All of your information has been a big help to me thus far.