Guttorm

A Giuking and murderer of Sigurd. According to the Volsunga Saga and the poems from the Poetic Edda, Guttorm was the son of Giuki and Grimhild. He was the brother of Gunnar, Hogni and Gudrun. But in Snorri Sturluson's Prose Edda, Guttorm was only Guiki's stepson, thus the half-brother of Gunnar, Hogni and Gudrun (also in The Song of Hyndla 27).

Gunnar and Hogni persuaded Guttorm to kill Sigurd, promising him wealth and power. Guttorm came upon Sigurd while the hero was sleeping with Gudrun. Guttorm mortally wounded Sigurd with his sword, but Sigurd killed Guttorm when he tried to flee. Sigurd threw his sword at Guttorm's back.