Hrungnir wagered with Odin that his horse Gullfaxi was faster than Sliepnir, staking his head on the outcome. When Sliepnir won the bet, Hrungnir attacked Odin, believing he was about to be killed.
Thor stepped up to subdue Hrungnir, fighting a famous duel. Seeing Hrungnir's skill in battle, once Thor prevailed, Odin said he would take what he was owed by conscripting him into the Einherjar.