Gjalp is a Jotunn, daughter of the Jotunn, Geirrod, and sister of Greip.

Magnus Chase and the Gods of Asgard

The Sword of Summer

Magnus and Sam go to her father's palace to find Mjølnir. The demigods claim guest rights so they will not be killed. Gjalp and Greip are killed by Magnus and Jack when they fail to make an agreement.