In 1385 DR, the Blue Breath of Change happened and destroyed the old fortress of Glaur, transporting Laerakond from the world of Abeir to the world of Toril. Prince Nathur Hethkantan's expedition to the fortress was obliterated, but Nathur himself survived as an spellscarred dracolich. Unable to leave the section of Glaur known as the Sapphire Vortex, Nathur conquered it and rename it the "Dominion of Bone", killing any creature who entered in his domain to create an army of undead servants. As of 1479 DR, "Dominion of Bone" bore a powerful army of undead whose mission was to find either the remains or at least a relic of the primordial Nehushta.
The Dominion of Bone was composed by undead created by Prince Nathur. The oldest among them were a few members of Nathur's original expedition that weren't assimilated into his body, but most members were either genasi of the Dominion of the Burned or adventurers who didn't survived their exploration of the Sapphire Vortex. The leader of the Dominion of Bone was Prince Nathur himself, and his most trusted servant was an skull lord named Teshaurus.