The illusion-king of the giants’ realm
The king of Útgarðr in the giants’ realm, a master of illusion. Thor and his companions visited his castle and were made fools of by a string of contests he set — yet every "defeat" was in truth an unbeatable illusion. With his illusions he showed Thor the limit of his own strength, and let the strongest god in Norse myth taste, for the first time, wit prevailing over brute force.
Útgarða-Loki had Thor’s company compete: Thor could not drain a drinking horn, whose end was in truth joined to the whole sea; he could not lift a grey cat, which was the serpent that girdles the world; he could not wrestle down an old woman, for she was Old Age itself. Afterward the giant king confessed the truth, then vanished with castle and all — what truly bested Thor was illusion, not brawn.
Below are how modern works borrow or reinterpret this name or story — not the original material. The two differ, so keep them apart.