The Crypt of Memory (5e)

From the introduction: Centuries ago, a group of elven separatists led by House Al-Dustriel and its matriarch Talkana Silumiel left the elven kingdom, allied with evil forces, and waged a civil war against their kin. House Al-Dustriel sought help from the dwarf kingdom of Liferock, which chose to remain neutral in the conflict. But the dwarven clan Ironflame, led by their Lord Lazaghan, defied the edict of their king and took up residence among the Kinslayer elves, forging weapons and armor for them during their civil war. Eventually the Kinslayers were defeated and the victorious elves returned Lazaghan and his clan to the dwarven king for justice. Lazaghan was sentenced to death and the rest of the clan was exiled. When Lazaghan was executed, the king gave his body to his clan, who interred him in a secret crypt.