Ratatosk

In Norse mythology, Ratatosk is the squirrel who runs up and down the world tree Yggdrasil and brings the messages of the eagle who sits at the top of the tree down to the dragon Nidhoggr who lives in the roots. Unfortunately, Ratatosk does not report the messages clearly and sows discord between the two.

John and Caitlin Matthews, The Element Encyclopaedia of Magical Creatures, 2013, Ratatosk, p 389