Heimdul was a warrior of the Vanir and part of a band of Vanir led by Bragi during a battle against a band of Æsir led by Wulfhere. Everyone on both sides were killed except for Heimdul and Conan (who had been part of Wulfhere's band before encountering Atali, the daughter of Ymir). Conan and Heimdul then fought each other, and Heimdul was slain.

The Vanirs are savages barbarians inhabiting the land of Vanaheim. They often battled against their cousins, the Æsir (Aesir). Their locks and beards are red as the blood on the sunlit snow. The Vanirs and the Æsir worship Ymir, the Frost Giant, who lives on the far northern mountains of Nordheim.
Nordheim extends as far north as any man has ever roamed, into vast and inhospitable tundras. One half of this country is Vanaheim on the shores of Western Ocean, bordering Pictish Wilderness southwest. The other is Asgard, bordering Hyperborea to the east. Cimmeria lies south, beyond the ice-capped Eiglophian Mountains.
The land of Nordheim is famed as a place of endless, trackless ice and snowy plains, a primal land bordered by mountains and limitless, borealis-tossed sky. There is only the white of snow and ice, and weather alternates between crisp stillness, moaning winds, and heavy snowfall, with naught else. Wind moans across the ice-crusted snow, bitingly cold, and the sun’s light is stark and bright, offering little comfort to man, beast, or plant. Little can thrive here, save for snow-furred monstrosities, and those who hunt them. That is what is said of Nordheim.

Map of the Hyborian age :