Froger
Saxo Grammaticus' Gesta Danorum (Book 4) speaks of Froger, the King of Norway, who was a great champion. Saxo relates:
According to some, he was the son of Odin, and when he begged the immortal gods to grant him a boon, received the privilege that no man should conquer him, save he who at the time of the conflict could catch up in his hand the dust lying beneath Froger's feet.
King Fródi the Active of Denmark, still a young man, learning of the charm, begged Froger to give him lessons in fighting. When the fighting court had been marked off, Fródi entered with glorious gold-hilted sword and clad in a golden breastplate and helmet. Fródi then begged a boon from Froger, that they might change positions and arms. Froger agreed. After the exchange, Fródi caught up some dust from where Froger had been standing and then quickly defeated Froger in battle and slew him.
Read more about this topic: Sons Of Odin