The demons possess a system similar to Yggdrasil, named Nidhogg. Both demons and goddesses possess the power to seal beings away. The demons also operate in a fashion similar to goddesses by creating contracts with humans and offering them wishes, but often at a price.
In Norse mythology, Nidhogg (Níðhöggr in Norse writting) is a dragon who knaws at the roots of the World Tree, Yggdrasill. Nidhogg is said to be controlled by the Norse goddess, Hel.