Call of Ragnarok
Each world also had significant places within. Valhalla is Odin’s hall located in Asgard. It was also home of the Einherjar, who were the souls of the greatest warriors. These warriors were selected by the Valkyries. The Einherjar would help defend the gods during Ragnarok.
These worlds are connected by Yggdrasil, the world tree, with Asgard at its top. Chewing at its roots in Niflheim is Nidhogg, a ferocious serpent or dragon. Asgard can be reached by Bifrost, a rainbow bridge guarded by Heimdall, a god who can see and hear for a hundred leagues.26