Heimdall was the king of the Dwarves in the Black Peaks region. He did not escape with the other Dwarven refugees when the Dragon Army sacked his lands, and over the decades many believed he was killed fighting the Red Dragon.
In a recent expedition to the Nichtgetan mine, however, a team of adventurers discovered that Heimdall survived the attack, and was enslaved for one hundred years. According to the Nichtgetan family's secret journals, Heimdall forged the sword Dragon Slayer, which the Nichtgetan then smuggled to Lord Stefan to win the great battle outside Threshold; the king was still alive six weeks ago, and is presumably still held captive by the remaining Dragon Army forces, deep in the Steachwarrens.
The news of Heimdall's likely survival has spread rapidly throughout the Dwarven diaspora; large numbers of Dwarves are mobilizing to take back their homeland from the remnants of the Dragon Army (and Lord Stefan if he gets in their way).