In Norse mythology, Fenrir is a monstrous wolf. Fenrir is attested in the Poetic Edda, compiled in the 13th century from earlier traditional sources, and the Prose Edda and Heimskringla, written in the 13th century by Snorri Sturluson. In both the Poetic Edda and Prose Edda, Fenrir is the father of the wolves Sköll and Hati Hróðvitnisson, and is a son of Loki. Upon the coming of Ragnarök, along with his sons devouring the moon and the sun, Fenrir is said to destroy the planet, his lower jaw reaching the earth, his upper jaw reaching the skies. It is foretold to kill the god Odin during Ragnarök, but will in turn be killed by Odin's son Víðarr.