Karvak, the damned

From Dungeons and dragons 4th edition quest "Pyramid of shadows"
Centuries ago, a tiefling wizard named Karavakos made a desperate bargain to secure his failing kingdom. Threatened by monsters and rebellion, he summoned a devil, gaining a legion of infernal soldiers who would obey him completely. The cost was simple: if he ever led them to defeat, they would abandon him and he would be doomed to eternal captivity. Only his own mistake could cause their downfall.
With this army, Karavakos conquered vast lands, building a powerful empire rivaling Nerath. In winter, he returned home with the eladrin princess Vyrellis, his bride-to-be, declaring they would rule together and soon conquer the Feywild.
When spring came, his armies entered the Feywild—but there, the devils lost their invincibility. Fey forces defeated them, breaking Karavakos’s pact and ending his ambitions. He was imprisoned in the Pyramid of Shadows alongside Vyrellis.
The pyramid, an infernal prison, shattered Karavakos’s life force into separate, free-willed fragments, preventing his escape. Enraged, he blamed Vyrellis for his failure, killed her, and cast her head into the pyramid’s depths.
Yet Vyrellis did not die. Her life force was also split, its pieces bound into gemstones and an orb scattered throughout the pyramid. Now, she seeks revenge against Karavakos and strives to reclaim her fragments to escape.