Hrungnir

Hrungnir is the mightiest of the giants, with a heart, head, and shield of solid stone. After winning a horse race against Odin on his steed Gullfaxi, he drinks deep in Asgard, boasts that he will sink it and carry off Freyja and Sif, and is challenged by Thor to a duel at Griotunagardar. The giants build a clay helper, Mokkurkalfi, beside him. Hrungnir hurls his great whetstone; Thor throws Mjolnir, which shatters it and splits the giant's skull. A fragment lodges in Thor's head, and the dead giant's leg pins the god until the boy Magni lifts it free.