Thiazi was a storm giant and kidnapper of Idunn.
With the aid of a magic eagle skin, Thiazi flew to Midgard where the gods Hœnir, Loki and Odin were cooking an ox. Still in the form of an eagle, he asked the gods for some of the meat. The gods agreed, but he ate so much that Loki became angry and impaled the eagle with a wooden staff. The eagle took flight with Loki still grasping the staff, unable to free himself. Thiazi released Loki on the condition that he would bring him the goddess Idunn and her apples of youth. Loki returned to Asgard and, a week later, went to the hall of Idunn and told her that he had found a tree in Midgard that bore golden apples like hers. He offered to show her the tree and together they crossed the rainbow bridge Bifröst and entered Midgard. Idunn carried her basket of apples as usual. Still in the form of a giant eagle, Thiazi swooped down and carried Idunn and her basket of golden apples to his fortress. Without the apples of youth the gods began to suffer the effects of old age. Loki soon fell under suspicion and admitted his role in the abduction of Idunn. The gods then threatened him with death if he failed to return Idunn and her apples to Asgard. Borrowing a magic falcon skin from the goddess Freyja, Loki assumed the form of a falcon, flew to Thiazi's fortress, located Idunn and transformed her into a nut. Then he took wing and began the long flight back to Asgard. When Thiazi returned to his stronghold he realized that Loki had taken Idunn and the apples of youth. Taking the form of an eagle, Thiazi flew after Loki as fast as he could. Thiazi was close behind Loki as the two birds neared the outer wall of Asgard. As soon as Loki flew over the wall, Odin ordered the gods to set fire to piles of wood and shavings. Thiazi's wings were badly burned, and he plunged to the ground where he was killed by the gods. Loki then returned Idunn and her apples to their normal form. Odin transformed the giant's eyes into two stars.