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.

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.

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.

The Thrice-Damned House of Thrune wants to seal the Inferno Gate, an uncontrolled portal to Hell, and the villainous adventurers are called to accomplish the task. To acquire the components and perform the ritual, they must first face down a hellspawn thieves' guild, the Hellknight Order of the Pike, and the knights of the Glorious Reclamation and their celestial allies. But before they can complete the ritual, the characters may be forced to examine their options—is closing the gate the best plan for the future? Will the villains obey their orders to close the gate to Hell—or might they make a deal with a devil for control of the portal? Or will they only become the latest in a long line of sacrifices to the Inferno Gate?

The knightly order known as the Glorious Reclamation continues its crusade against diabolic Cheliax, conquering the town of Kantaria, where the goddess Iomedae once ruled as a mortal. The villainous adventurers, now official agents of House Thrune, must retake the town, depriving the knights of a valuable holy site. Can the evil characters earn greater infamy and prestige by dealing the Glorious Reclamation a serious defeat in their most substantial territorial gain so far, or will the knights' rebellion continue unchecked across Cheliax?

Cheliax's largest city, Westcrown, has fallen to the Glorious Reclamation, and the evil adventurers are sent to reclaim the metropolis in the name of House Thrune. Armed with the legendary weapon they created from a gold dragon's head, the nefarious characters confront the Glorious Reclamation's forces and break its siege of a nearby Hellknight citadel. Once the army is defeated, the villains enter Westcrown, where they must undermine the chivalrous knights' rule of the city. Finally, they face the founder and Lord Marshal of the Glorious Reclamation to end the rebellion and restore the Thrice-Damned House of Thrune's rule over the empire of Cheliax.