Thrud was promised to Alvis, a dwarf, in exchange for which Alvis made weapons for the gods. Thor devised a plan to stop Alvis from marrying his daughter. He told Alvis that, because of his small height, he had to prove his wisdom. Alvis agreed and Thor made the tests last until after the sun had risen--all dwarves turned to stone when exposed to sunlight, so Alvis was petrified and Thrud remained unmarried.