Skadi, or Skade (which literally means hurt/pain), was a giantess (a jotun) - the goddess of winter, skiing and hunting.
Skadi was the daughter of Thiazi, a jotun who fell in with the gods and was slain by them. Filled with lust for revenge, Skadi went to Asgard and demanded to marry one of them as payment for her father's death. She had her eye on the beautiful Balder.
The Aesir accepted her demand, but on one condition: That she would only be allowed to look at their feet when choosing her mate. She did, and picked the most beautiful feet she could find, convinced that they had to be Balder's feet, but the feet belonged to Njord, a much older man.
Not satisfied, she put out a new demand: The Aesir would now have to make her laugh to make friends. Many tried to amuse her, but all failed until Loki came up with an idea. He tied a rope between the beard of a goat and his own private parts, and they started pulling in opposite directions, both screaming in pain. This made Skadi laugh, and the treaty was signed, so to speak. (This is, by the way, an example of how Loki is not an evil god, just a prankster and a trickster with more imagination than what is good for him.)
Njord and Skadi got married, but their marriage was not a happy one. They couldn't even decide where to live, in Thiazi's castle Thrymheim or in Njord's palace Noatun. Eventually, they broke up, and Skadi married Ull.
Childhood reading of Norse Mythology