giant
Mökkurkálfi
The clay giant, nine miles tall, built by the giants to stand with Hrungnir against Thor. He has a mare's heart, wets himself in fear, and falls to Thor's servant Þjálfi.
Mökkurkálfi exists only in Snorri's account of Hrungnir's duel in Skáldskaparmál Skáldskaparmál 17, and Snorri gives him just a few lines. The giants fear what Thor will do to them if their strongest champion dies, so they build a man of clay at Grjótúnagarðr, "nine miles high and three broad under the arm-pits". No heart is big enough for him until they use a mare's.
It does not help. As Thor approaches, the clay giant "was sore afraid, and it is said that he wet himself". Þjálfi strikes him down, and he falls "with little glory" Skáldskaparmál 17.
Snorri gives no source for this part of the story. The Haustlöng stanzas he quotes do not mention a clay giant, so whether Mökkurkálfi belongs to older tradition or is Snorri's own addition cannot be known.
In the sources
Quoted from the hosted translations; each line is checked against the text when the site is built. Select a reference to read it in context.
Then the giants made a man of clay at Grjótúnagard: he was nine miles high and three broad under the arm-pits
they could get no heart big enough to fit him, until they took one from a mare
Thjálfi struck at Mökkurkálfi, and he fell with little glory
