I am a student of Northern European/Old Icelandic Seidr. What I find particularly fascinating in my studies are not the deities but rather the creatures living on the World Tree along with the Primordial Giants who predated the gods.
One such creature is Níðhöggr, the “Derision Striker.” Níðhöggr is a great dragon who lives at the base of Yggdrasil, the World Tree. She gnaws on the roots of the tree, stimulating new growth. Her home stretches from icy Niflheim, near what is called the “Roaring Kettle”, the sacred well of all the rivers of Niflheim, all the way to Dead Man’s Shore in Helheim where she devours the piled corpses.