In the town of Easthaven, a group of adventurers is tasked on a routine mission to resupply an expedition to the Reghed Glacier. But everything is not quite as it seems, and it's not long before the chronographer's misfortunes become apparent.

This adventure is written with the intent that it takes place in the subterranean world called the Underdark in the world of Forgotten Realms, although it may be placed in other settings. Within the Underdark, Cyrog's lair can be placed anywhere though it is stated to be thousands of miles east of Gravenhollow. If you are running Out of the Abyss, you may want to have your players see the vision Cyrog Lives! Hail Orcus! (OOTA, 158). Additionally, it is recommended that this adventure be used for a party of 4 to 6 players, level 9 to 12. While merely hinted at through visions in Out of the Abyss, Orcus is roaming the Underdark unchallenged with an army of mind flayers at his disposal. Cyrog, the elder brain of a mind flayer colony in the Underdark has died. The demon lord Orcus has reanimated and taken control of it. The hive of mind flayers is now bent to Orcus's will through Cyrog as he strives to make all life in the multiverse into a vast undead horde under his control. The adventurers are contacted by a patron who gives them a special item (such as brain worms) to suppress their brain waves and make it possible to infiltrate the Cyrog's Lair without immediate detection. The adventurers must defeat or otherwise subdue mind flayers and a few guards, override the elder brain's mechanical defense system, and slay Cyrog.

For ages, “the old monastery on the hill” was simply that and nothing more to those that knew of it – a small building of a forgotten age and purpose, overgrown by the land around it. But recently, rumors have been making way among the educated that there is a wealth of knowledge that hides within the old monastery, waiting for someone to find it. Most dismissed these rumors as hearsay... but those with their eyes on the prize continued to pay attention. There must have been some merit to these claims, because seemingly overnight a monstrous creature has appeared on the monastery grounds - a serpent the size of a dragon, with a dozen legs and breath that crackles with lightning! There's no doubt the rumors and the monster's appearance are related somehow, and the PCs are tasked to put their skills to work to figure it out!