An ancient, eldritch tablet the heroes recovered during their previous adventure needs translating. However, when they take it to an expert for help, cultists of Azathoth attempt to steal the object for their own sinister purposes. After dealing with the zealots and deciphering the relic, the heroes learn of another deep-sun locale called Ezorod and the evil elder entity that has its attention focused there. With the tablet in hand, the heroes have the map and the key to Ezorod, allowing them to enter the place and explore it. Within this lightless oubliette, the heroes face ghastly creatures and find magical technology that could advance sun diving by leaps. Taking it destabilizes Ezorod, and as the PCs escape the solar dungeon, they receive a mysterious message that heralds a future confrontation!