Zhaitan

Zhaitan is the Elder Undead Dragon of Orr. The name is known to the races of Tyria primarily via dwarven legends. Zhaitan's spheres of influence are shadow and death.
 Zhaitan, like the other Elder Dragons, is thought to have last awakened 10,000 years ago, around the time of the disappearance of the Giganticus Lupicus, and then fallen back into slumber from consuming all life they could find. For more than a millennium, it rested beneath the land that would become the Kingdom of Orr. When the Six Human Gods revoked the gift of magic back into the Bloodstone to split it into the familiar four schools in 1 BE, they tapped into the dormant dragon's energy and increased the power of magic in doing so, not knowing of Zhaitan's existence.