Sköll & Hati

Norse myth explains the movement of the sun and moon as flight. Sól and Máni do not simply travel; they are driven, because two wolves are always behind them.
Grímnismál names them: Skǫll is the wolf that follows the bright-faced god to the shelter of the wood, and Hati, Hróðvitnir's son, goes before the bright bride of heaven. The bright-faced god is the sun, and the bride of heaven is most likely the sun too: even Snorri, who gives Hati the moon, has him run in front of the sun. The poem itself never mentions the moon. Snorri tidies this into the version most people know, one wolf for the sun, one for the moon, but the older poem is less symmetrical than the retelling, and it is worth saying so.
The chase has an end. Völuspá foretells that one of Fenrir's brood will become a snatcher of the moon in troll's shape, and that the sunshine will turn black. Snorri says plainly that the wolves will finally catch what they pursue, and in his account of Ragnarök the wolf swallows the sun and the other wolf takes the moon. That is the point of the image: not decoration for day and night, but a countdown running under the ordinary sky.
Their parentage is inferred rather than stated. Hati's patronymic, Hróðvitnisson, points to Hróðvitnir, a byname of Fenrir, and Snorri says these wolves come from the brood a giantess bears in the Ironwood, the brood Völuspá calls Fenris kindir, Fenrir's kin. Skǫll is never given a father. Reading Skǫll and Hati as Fenrir's offspring is reasonable, and it is still a reading.
Note on our figure: the sun in the original drawing carried an interlaced square knot on a solar disc. It is a genuine Nordic knot form, but on a rayed disc it can be misread by people who do not know the difference, so we redrew the sun as a plain outline. The wolves are untouched.