"Hymir!" a youthful voice called from outside the giant's cave. Hymir poked his head out, and saw, indeed, the youthful owner of the voice. "Hymir, O Mighty Giant! I am in need of shelter, and your hospitality is known far and wide!"
Hymir consented, unafraid of humans, and the young man stayed the night. After a dinner of roasted mutton and fried potatoes, the young man spent the night, wrapped in sheepskins near the entrance of the cave. In the morning, Hymir rose early, and the youth rose, too. "Where are you going?" he asked his host.
"I am going fishing in the deep sea," the giant growled.
The youth grinned broadly. "Take me with you! I shall catch and cook for you the biggest fish you have ever seen, as thanks for your hospitality!"
The giant doubtfully eyed the frail youth. "You will catch cold," he grumbled. "I sit far out in the ocean, for many hours. You will not survive." But the young man was persistent, and assured the giant that he could row further than the giant could, and would last longer than his host. He was so insistent and boastful that Hymir allowed him to come, if only to prove him wrong.
"What do I take as bait?" the youth asked.
"Find your own," the giant replied, curtly. "I am not your mother!"
The youth, seeing Hymir's herd of oxen grazing outside of the cave, struck off the head of the largest and heaved it onto the boat (for the youth had a plan to catch something larger than a fish). Once settled into the boat, the youth began to row. And row. And row. He rowed so far out into the ocean, that Hymir was afraid that they would fall prey to Jormungand, the Midgard Serpent, who lived at the bottom of the sea and circled the entire earth.
But the youth paid no attention to Hymir's entreaties to turn back and, instead, baited his hook with the ox head. Casting it into the sea, the youth waited. At long last, the line began to thrash, the ocean began to roll, and the enormous head of the Midgard Serpent emerged from the waters, hissing angrily, poisonous vapors issuing forth from its mouth.
The youth stood, shouting triumphantly, and in that moment his disguise dissolved and he was revealed to be Thor, the god of thunder. Thor raised Mjolnir, his hammer, ready to deal a fatal blow to Jormungand (for it had been predicted that Thor and Jormungand would fight to the death at Ragnarok, the end of all things, and Thor wished to avoid this).
Hymir, seeing Thor and Jormungand, feared that Ragnarok was upon them. He grabbed his knife and cut the line, and the serpent sank back into the sea. Thor threw his hammer after it, but to no avail. Then, angry at the giant's meddling, Thor knocked Hymir in the ear so hard that the giant fell backwards into the water. Thor himself returned to the shore, sullen at his defeat.
-Norse Myth
