Magni was the Norse god of strength — a son of Thor so mighty that, while still a child of three nights old, he alone could lift the leg of a fallen giant off his pinned father. His very name means “strength,” and he is fated, with his brother Modi, to inherit Thor's great hammer and survive into the new world after Ragnarök.
The Mighty Child
Magni (Old Norse Magni, “the mighty,” “strength”) was a son of Thor by the giantess Járnsaxa, and from his birth he embodied the sheer physical power of his father, the strongest of the gods. His strength was prodigious and precocious, the inherited might of the thunder-god distilled into a single attribute — for where Thor was a god of many aspects, Magni was strength itself, the next generation's vessel of the power that defended gods and men against the giants.
The Lifting of Hrungnir's Leg
Magni's great deed came when he was astonishingly young. After Thor slew the giant Hrungnir in single combat, the dead giant fell with one enormous leg pinning Thor to the ground, and the mightiest of the gods lay trapped, unable to free himself, while the other gods tried and failed to lift the colossal limb. Then came Magni — only three nights old — who took hold of the giant's leg and heaved it off his father with ease, freeing Thor where all the grown gods had failed. Thor, amazed and proud, praised his infant son and gave him the giant's great horse Gullfaxi (“golden-mane”) as a reward — to Odin's displeasure, for the All-Father felt the prize should have been his. The deed marked Magni at once as a worthy heir to his father's strength.
The Heir of the Hammer
Magni's destiny lies beyond the end of the world. It is foretold that at Ragnarök, when Thor falls slaying the world-serpent and the old gods perish, Magni and his brother Modi will be among the survivors — and that they will inherit Mjölnir, their father's mighty hammer, carrying it into the new and cleansed world that rises from the ruins. Thus the great weapon that defended the gods does not perish with Thor but passes to his strong sons, who will bear it in the age to come.
The Strength That Survives
Magni endures as the personification of strength and the heir of Thor — the prodigiously mighty child who freed his trapped father, the son who carries the thunder-god's power into the future. He embodies the Norse hope woven into the doom of Ragnarök: that strength itself does not die with the old world, that the hammer that warded off chaos will be borne again by a new generation, and that the might of Thor lives on in his sons after the gods themselves have fallen.
At three nights old he lifted a dead giant's leg off his pinned father when all the grown gods had failed — and after the world ends, he and his brother will carry their father's hammer into the age reborn.