In The Days of Giants A Book of Norse Tales
Page: 16"Mighty man," quoth he, "we are willing to agree to your price—upon one condition. It is too long a time that you ask; we cannot wait three half-years for our castle; that is equal to three centuries when one is in a hurry. See that you finish the fort without help in one winter, one short winter, and you shall have fair Freia with the Sun and Moon. But if, on the first day of summer, one stone is wanting to the walls, or if any one has42 given you aid in the building, then your reward is lost, and you shall depart without payment." So spoke Loki, in the name of all the gods; but the plan was his own.
At first the stranger shook his head and frowned, saying that in so short a time no one unaided could complete the undertaking. At last he made another offer. "Let me have but my good horse to help me, and I will try," he urged. "Let me bring the useful Svadilföri with me to the task, and I will finish the work in one winter of short days, or lose my reward. Surely, you will not deny me this little help, from one four-footed friend."
Then again the Æsir consulted, and the wiser of them were doubtful whether it were best to accept the stranger's offer so strangely made. But again Loki urged them to accept. "Surely, there is no harm," he said. "Even with his old horse to help him, he cannot build the castle in the promised time. We shall gain a fortress without trouble and with never a price to pay."
Loki was so eager that, although the other Æsir did not like this crafty way of making43 bargains, they finally consented. Then in the presence of the heroes, with the Valkyries and Mimer's head for witnesses, the stranger and the Æsir gave solemn promise that the bargain should be kept.
On the first day of winter the strange builder began his work, and wondrous was the way he set about it. His strength seemed as the strength of a hundred men. As for his horse Svadilföri, he did more work by half than even the mighty builder. In the night he dragged the enormous rocks that were to be used in building the castle, rocks as big as mountains of the earth; while in the daytime the stranger piled them into place with his iron arms.