The Hell's Vengeance Adventure Path begins with "The Hellfire Compact," an exciting new adventure in which the players take the roles of evil characters in the diabolical empire of Cheliax! A paladin of Iomedae and knight-errant of the Glorious Reclamation comes to the town of Longacre, inspiring the citizens to join the uprising against the Thrice-Damned House of Thrune. First as amoral mercenaries, then as retainers of the wicked archbaron of Longacre, the evil adventurers must move quickly to put down the insurgency and keep the town from falling to the knight's rebellion.

Her Infernal Majestrix Queen Abrogail II of Cheliax summons her agents to the city of Egorian to address the current crisis with the Glorious Reclamation. Upon arriving in the bustling capital, the adventurers find themselves swept up in the cutthroat politics of the imperial court. To impress the queen and secure a royal audience, the wicked characters must scour the City of Thorns to root out and eradicate a secret organization that works to free halfling slaves. But to truly earn Queen Abrogail's trust, the adventurers must perform a sacrifice for the queen to renew House Thrune's contract with Hell, and there are many—both within the court and without—who wish to see the monarch dethroned.

Now bound to Queen Abrogail by infernal contracts, the villainous adventurers are tasked with destroying the Glorious Reclamation's headquarters in the former citadel of the Hellknight Order of the Godclaw, where they face a gold dragon ally of Iomedae herself! Only if they can survive the terrible onslaught of this fearsome foe and secure the citadel from the revolutionaries can the vile characters succeed at their quest—to perform an evil ritual, using the dragon's head to craft a legendary weapon capable of defeating the Glorious Reclamation's army of valorous knights once and for all.