Sköll in the context of Sól (Sun)

Fenrir (Old Norse 'fen-dweller') or Fenrisúlfr (Old Norse "Fenrir's wolf", often translated "Fenris-wolf"), also referred to as Hróðvitnir (Old Norse "fame-wolf") and Vánagandr (Old Norse 'monster of the [River] Ván'), is a monstrous wolf in Norse mythology. In Old Norse texts, Fenrir plays a key role during the events of Ragnarök, where he is foretold to assist in setting the world aflame, resulting in the collapse of humanity and society, and killing the god Odin.

Fenrir, along with Hel and Jörmungandr, is a child of Loki and female jötunn Angrboða. He is attested in the Poetic Edda, compiled in the 13th century from earlier traditional sources, and the Prose Edda and Heimskringla, composed in the 13th century. In both the Poetic Edda and Prose Edda, Fenrir is the father of the wolves Sköll and Hati Hróðvitnisson, is a son of Loki and is foretold to kill the god Odin during the events of Ragnarök, but will in turn be killed by Odin's son Víðarr.

In Norse mythology, Hati Hróðvitnisson (first name meaning "He Who Hates", or "Enemy") is a warg; a wolf that, according to Snorri Sturluson's Prose Edda, chases Máni, the Moon, across the night sky, just as the wolf Sköll chases Sól, the Sun, during the day, until the time of Ragnarök, when they will swallow these heavenly bodies. Snorri also gives another name for a wolf who swallows the Moon, Mánagarmr ([ˈmɑːnɑˌɡɑrmz̠], "Moon-Hound", or "Moon's Dog").

Hati's patronymic Hróðvitnisson, attested in both the Eddic poem "Grímnismál" and the Gylfaginning section of the Prose Edda, indicates that he is the son of Fenrir, for whom Hróðvitnir ("Famous Wolf") is an alternate name. According to Snorri, Hati's mother is the giantess, not named but mentioned in the Eddic poem "Völuspá", who dwells to the east of Midgard in the forest of Járnviðr ("Ironwood") and "fosters Fenrir's kin". Snorri states that this giantess and witch bears many giants for sons, all in the form of wolves, including Hati and Sköll, who is thus implied to be Hati's brother. In two verses of "Völuspá" that Snorri cites, an unnamed son of this giantess is prophesied to snatch the Moon, and also eat the flesh of the dead, spattering the heavens with blood. In contrast the Eddic poem "Vafþrúðnismál" states that Fenrir himself will destroy the sun.