After the walls of Asgard, the heavenly dwelling-place of the Norse gods, were reduced to rubble during a war, the gods were reluctant to take on the task of rebuilding. One day a giant, disguised as a stonemason, arrived to present a proposal to the gods. He would build new walls to surround the city, stronger and higher than before. In return, he would take the Sun, the Moon, and the hand of Freyja, the goddess of love and beauty, in marriage.

The gods were outraged, but Loki, the god of discord and mischief, suggested they offer the stonemason a counter proposal. He could have his price, but only if he could complete the task in the six months from the winter to the summer solstice and with the aid of no man. If he failed, he would receive nothing.

The disguised giant agreed, provided he could have the help of his stallion, Sval∂ifarí. The deal was struck and the stonemason began construction by gathering massive slabs of stone and boulders and loading them into a net hitched to Sval∂ifarí, who then hauled them up the hill and helped to hoist them into place. When the gods saw how much work had been accomplished in just one night, they were furious because it was obvious that the stonemason wasn’t a mortal man but a giant. However, since this was not prohibited in the contract, they could do nothing.

As the summer solstice approached and the walls neared completion, the possibility of them being completed on time looked more and more likely. The gods began to worry that the stonemason would meet his deadline and so they made Loki responsible for foiling him since he had been the one who talked them into the giant’s proposal in the first place.

The next evening, Loki transformed himself into a beautiful mare and appeared before Sval∂ifarí who was overcome with desire and abandoned his master and his labors. Sval∂ifarí chased the mare all night, causing the stonemason to leave his work to pursue his horse, putting him at risk to lose his bargain with the gods. In his anger, he revealed himself as a giant, not a man. The gods sent for Thor, the god of thunder and rain and farming, who dispatched the giant with his hammer.

Loki could not elude the smitten stallion, however, and reappeared many months later with the eight-legged horse, Sleipnir, the result of his union with Sval∂ifarí. Sleipnir became the first of all the horses and the magical steed of Odin, the supreme god of wisdom and war.