Ratatoskr

In Norse mythology, Ratatoskr is a squirrel who runs up and down the world tree Yggdrasil, carrying messages between an eagle perched atop the tree and the dragon Nidhogg, who dwells beneath one of its roots and is already recorded in this atlas. Ratatoskr is attested in the Poetic Edda, compiled in the 13th century from earlier traditional sources, and in the Prose Edda, written in the 13th century by the Icelandic scholar Snorri Sturluson. His name is generally understood to mean drill-tooth or bore-tooth.