Ratatoskr

Ratatoskr, the Messenger, is a squirrel that spends its life carrying messages between the duo of the Unnamed Eagle and the hawk Vethrfolnir, perched at the top of the World Tree Yggdrasil, and Nidhogg, the dragon that lives in the roots of the Tree.

In the game, Ratatoskr can be spotted a few times in the Vethrfolnir's Perch level, scurrying up and down the trunk of Yggdrasil. He is massive for a squirrel, being many times the size of a human.