Prince Jon was a world's renowned Viking warrior who lived in Scandinavia during the early in the 10th Century.
After standing on a frozen battlefield as the last survivor of a long forgotten war, Prince Jon met and fell in love with a Valkyrie. Odin, king of the Norse Gods discovered the affair and banished Jon from Valhalla, saying that the only way he could return to be reunited with his love was to die a heroic death. However, Odin gifted the Viking Prince with invulnerability from harm by metal, wood, fire and water, thereby preventing him from dying in combat.
After many years traveling the world, searching for his heroic death, The Viking Prince gradually grew distant from humanity and eventually tired of the endless battles and so he sailed into the frozen north, where he passed out of living memory. The Amazons of Themyscira knew of the story.
More than a thousand years later, his body was discovered inside his ship, frozen in the side of a melting glacier. The Legion of Doom learned of the Viking Prince's re-discovery and sought to capture his body to learn the secret of invulnerability. The Justice League managed to thwart the plan; Wonder Woman decided to give the Prince a proper funeral according to Viking tradition and sent his body into the sun along with his ship.