Thiazi was a powerful Norse giant who took eagle form — the jötunn who abducted the goddess Idun and her apples of immortality, bringing the gods to the edge of decay, and the father of the giantess Skadi. His theft of the goddess of youth and his fiery death are among the most consequential of the giant-tales, and his eyes were set in the sky as stars.
The Eagle-Giant
Thiazi (Old Norse &Th;jaźi) was a mighty and wealthy giant, the son of the giant Ölvaldi, and the father of the future goddess Skadi. He possessed an eagle-cloak (or the power to take eagle form), and in this shape he was a formidable and dangerous being, able to fly and to seize his prey from the sky. He dwelt in a great hall called Thrymheim in the mountains of the giants' land.
The Abduction of Idun
Thiazi's great deed was the theft of Idun and her golden apples of youth. He caught Loki in a vulnerable moment (having seized him in eagle form during a journey) and forced Loki to swear that he would deliver the goddess Idun out of Asgard. Loki, to save himself, lured Idun into the forest with a trick — and Thiazi, in eagle form, swooped down and carried her and her apples away to Thrymheim. Deprived of Idun's apples of immortality, the gods began to age and wither, greying and failing, until they discovered Loki's treachery and forced him, on pain of death, to bring Idun back.
The Fiery Death
Loki borrowed Freya's falcon cloak, flew to Thrymheim, found Idun alone, transformed her into a nut, and flew back toward Asgard with her in his talons. Thiazi, returning to find Idun gone, took eagle form and gave furious chase, the two birds streaking across the sky. As Loki neared Asgard, the gods kindled a great bonfire upon the walls; Loki shot over the flames safely, but the pursuing eagle Thiazi, flying too fast to stop, was caught by the fire, his feathers blazed up, and he fell to the ground within Asgard, where the waiting gods killed him. Thus the eagle-giant met his end in fire, undone by the very trickster who had served him.
The Eyes Among the Stars
Thiazi's death had a famous aftermath. His daughter Skadi armed herself and marched on Asgard to avenge her father; the gods made peace with her by offering her a husband (she chose Njord) and by making her laugh (Loki managed it), and — as part of the settlement — Odin took Thiazi's eyes and cast them up into the heavens, where they became two stars, an everlasting memorial to the slain giant. Thiazi endures as one of the most important of the Norse giants — the eagle-giant whose theft of Idun nearly aged the gods to death, the father of Skadi, and the jötunn whose eyes shine still among the stars.
He stole the goddess of youth and nearly let the gods wither into age — and when he burned to death chasing her back, his eyes were flung into the sky to shine forever as stars.