Once upon a time, when the gods were building their abodes, a certain
builder came and offered to erect them, in the space of three
half-years, a city so well fortified that they should be quite safe in
it from the incursions of the forest-giants and the giants of the
mountains, even although these foes should have already penetrated
within the enclosure Midgard. He asked, however, for his reward, the
goddess Freyja, together with the sun and moon. The gods thought over
the matter a long while, and at length agreed to his terms, on the
understanding that he would finish the whole work himself without any
one's assistance, and that all was to be finished within the space of
one single winter. If anything remained to be done when the first day of
summer came, the builder was to entirely forfeit the reward agreed on.
When the builder was told this he asked that he might be allowed the use
of his horse, Svadilfari, and to this the gods, by the advice of Loki,
agreed.

On the first day of winter the builder set to work, and during the night
he caused his horse to draw stones for the building. The gods beheld
with astonishment the extraordinary size of these, and marked with
wonder that the horse did much more work than his master. The contract
between them and the giant had, however, been confirmed with many oaths
and in the presence of many witnesses, for without such a precaution a
giant would not have trusted himself among the gods, especially at a
time when Thor was returning from an expedition he had made into the
east against the giants.

The winter was far advanced, and towards its end the city had been built
so strongly and so lofty as to be almost secure. The time was nearly
expired, only three days remaining, and nothing was wanted to complete
the work save the gates, which were not yet put up. The gods then began
to deliberate, and to ask one another who it was that had advised that
Freyja should be given to one who dwelt in Jotunheim, and that they
should plunge the heavens in darkness by allowing one to carry away with
him the sun and moon. They all agreed that only Loki could have given
such bad counsel, and that it would be only just to either make him
contrive some way or other to prevent the builder accomplishing his work
and having a right to claim his reward, or to put him to death. They at
once laid hands on Loki, who, in his fright, promised upon oath to do
what they desired, let it cost him what it might.

That very night, while the builder was employing his horse to convey
stones, a mare suddenly ran out of a neighbouring forest and commenced
to neigh. The horse broke loose and ran after the mare into the forest,
and the builder ran after his horse.

Between one thing and another the whole night was lost, so that when day
broke the work was not completed.

The builder, recognising that he could by no means finish his task,
took again his giant form; and the gods, seeing that it was a
mountain-giant with whom they had to deal, feeling that their oath did
not bind them, called on Thor. He at once ran to them, and paid the
builder his fee with a blow of his hammer which shattered his skull to
pieces and threw him down headlong into Niflhel.

The horse Sleipner comes of the horse Svadilfari, and it excels all
others possessed by gods or men.