Glámr by Sabine Baring-Gould

The following story is found in the Gretla, an Icelandic Saga, composed in the thirteenth century, or that comes to us in the form then given to it; but it is a redaction of a Saga of much earlier date. Most of it is thoroughly historical, and its statements are corroborated by other Sagas. The following incident was introduced to account for the fact that the outlaw Grettir would run any risk rather than spend the long winter nights alone in the dark.

At the beginning of the eleventh century there stood, a little way up the Valley of Shadows in the north of Iceland, a small farm, occupied by a worthy bonder, named Thorhall, and his wife. The farmer was not exactly a chieftain, but he was well enough connected to be considered respectable; to back up his gentility he possessed numerous flocks of sheep and a goodly drove of oxen. Thorhall would have been a happy man but for one circumstance -- his sheepwalks were haunted.