Thialfi and his sister, Roska, lived with their father and their mother on a farm at the edge of the wild country. There were monsters beyond the farm that Thialfi had to outrun, but fortunately, he could outrun anyone or anything. One day, Loki and Thor visited from Asgard, arriving in a chariot pulled by two goats. They expected lodging and food for the night, but Thialfi had none. So they killed both goats and skinned their corpses. Loki convinced Thialfi that the bone marrow of the goat would make him strong, even though thor instructed them not to eat the marrow, only the meat. Once Thor had his backed turned, Thialfi ate the marrow and hid it under the undamaged bones.
once Thor used his hammer to then revive the two goats from the bone marrow, he soon noticed one of them had a broken leg. When confronted, Thialfi confessed, and Thor agreed to spare Thialfi's family if he became his bondservant. Thor, Loki and Thialfi then traveled east, looking for shelter once it grew cold, and stumbled upon an oddly shaped house where Loki and Thialfi slept, and Thor kept watch for a sudden noise. Growing tired of the noise, Thor went off to find the source. It was then that he found a large giant, Skrymir, sleeping and that the house was not a house at all, but a glove of the giant's.
Skrymir have suggested that they travel alongside him, which they did, having him carry their provisions in his bag. Loki and Thir attempted to open this bag, but neither could. Thor attempted to wake the giant by using his hammer to slam against his forehead. but to avail, he hadn't woken up until the next morning. when they had, they began traveling once again, stumbled upon this fortress while passing through Jotunheim.
the place they happened to stumbled upon was actually Utgard, led by another giant by the name of Utgardaloki. Utgardaloki knew of the three and asked each of their abilities. He had Loki attempt an eating competition with his servant, Logi. They ate at the same speed, but Logi ate the bones and flesh. He had Thialfi race against Hugi, but Thialfi lost each time. He then had Thor drink from the drinking horn, which did not empty no matter how hard Thor tried. Thor also tried to lift Utgardaloki's cat, but could hardly lift a paw. He also wrestled Utgardaloki's old nurse but lost as she had him on one knee.
though once each had failed to overcome their competition, they were asked how they enjoyed their stay. all said that they hadn't enjoyed it much, having their pride damaged by failing each challenge. Utgardaloki then revealed that he had been Skrymir the whole time, and all of this had been an illusion. He put mountains between his head and Thor when Thor has used his hammer to wake Skrymir. Loki was actually going up against fire, Thialfi against thought, and Thor against the deepest part of the sea and Jormungundr, the serpent and old age. All had actually done outstanding jobs, and that scared Skrymir that they'd destroy Utgard.
Skrymir went on to explain that he plans on defending Utgard and his fortress from them in the future, by which he stated that he was going to make sure that neither of them was to see or return to Utgard again. Thor went to raise his hammer above his head and strike, but Utgardaloki was gone along with the fortress. So the three went to head back to home and that was that.