Tomb of Horrors
The Tomb of Horrors, hidden in the mountains north of Silverstone, is an infamous destination for adventurers seeking glory, treasure, or evils to smite. While many declared their intent to cleanse the Tomb of its evil over the years, only one band of adventurers ever returned alive.
The Tomb was created by the demilich Acererak, a devotee of Nerull, and the entire dungeon functions as a massive altar to the god of death, and gains power from the souls of those who perish within. It was theorized that Acererak sought to use its power to become an exarch of Nerull, but with Nerull's death it is unknown whether Acererak's goals changed.
In 2959 the Challengers of the Unspeakable entered the Tomb of Horrors at the behest of Theriana, emerging successfully a few days later with Acererak's soul gems. The Tomb has lain dormant ever since, though whispers persist that Acererak will someday return...