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 making 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. The Æsir watched him with amazement; never was seen such strength in Asgard. Neither Tŷr the stout nor Thor the strong could match the power of the stranger. The gods began to look at one another uneasily. Who was this mighty one who had come among them, and what if after all he should win his reward? Freia trembled in her palace, and the Sun and Moon grew dim with fear. Still the work went on, and the fort was piling higher and higher, by day and by night. There were but three days left before the end of winter, and already the building was so tall and so strong that it was safe from the attacks of any giant. The Æsir were delighted with their fine new castle; but their pride was dimmed by the fear that it must be paid for at all too costly a price. For only the gateway remained to be completed, and unless the stranger should fail to finish that in the next three days, they must give him Freia with the Sun and Moon.