Publisher's blurb: Deep in the Underdark, an elder brain Cyrog has died and been reanimated by the Demon Prince of Undeath, Orcus. Brave adventurers will be called upon to help vanquish this evil. Should they fail, Cyrog and all of his mind flayers will be able to create an army for Orcus to unleash destruction upon the Underdark and the world. In this supplement to Out of the Abyss, your party will explore the lair of an elder brain named Cyrog (aluded to in the official adventure, but never fleshed out). The adventure hooks are primarily linked to Out of the Abyss, but the story may be run as a standalone adventure as well. The adventure contains opportunities for roleplay, exploration, and combat.