Yrim

Yrim is an enormous serpent that slithers among the roots of the Weltbaum - a huge tree in Fallsmar that models the Nine Realms. He also appeared in a deep chasm at the entrance to Niflheim after Kaleb stepped through the portal to that realm.
The serpent told him that if he was not dead, there would be no entry into Niflheim for him. Then Yrim swallowed him, and the next thing he knew, he awoke, alive, on a branch of the tree.