When an unlucky historian in Absalom uncovers an infernal book from distant Tian Xia, he unwittingly unleashes a terrible evil into the city—the legions of devils imprisoned within its dusty pages. Only the book’s holy counterpart can end the threat, and the Varlokkur have been called in to assist. Can the Agents locate and retrieve the key to ending the diabolical invasion of the City at the Center of the World, or will Absalom be drowned in the sea of destruction wrought by the Infernal Incantation?
Following their ventures into Delirium’s Tangle, the agents take several weeks of time to rest and recover. Thanks to Behnams curative magic, Albert recovers relatively quickly from the madness that consumed him within the Tangle, but it is clear that the experience has scarred the wizard. Upon his recovery, Albert spends a great deal of time investigating Maglor Narmolanya, the new head of the Freedom Phalanx. By following some of the elves new recruits, he is able to learn that Maglor has access to one of the planar portal within the Spire of Nex, and has been sending under qualified adventurers inside. Albert persuades the group he followed to abandon their mission, but provokes Maglor by doing so and receives a clear warning to back off.
Meanwhile, many of the agents investigate the growing number of murders in Absalom. Learning that only female members of the clergy are being targeted and that Cheliax has dispatched a number of inquisitors and Hellknights to locate the killer. When the group are able to share this information, they conclude that they may need to go behind Alexis’ back to delve deeper into what is happening.
After several weeks apart, the agents reunite to celebrate Behnams elevation within his church. They attend a small morning ceremony where the young cleric is ordained as a Light of the Dawnflower. After feeling the touch of the Everlight, Behnam rejoins the other heroes to meet with Alexis.
The diviner informs the operatives that news has reached him that Yargos Gill, the historian that assisted them with the Silent Tide, is in trouble. According to his aide, Yargos had been researching a tome called the Infernal Incantation at the behest of Andoran benefactors and in doing so has potentially unleashed the horde of devils contained within the book on Absalom. Alexis entrusts the agents to help Yargos and resolve the situation as quickly as possible.
The group quickly make their way to Yargos newly appointed townhouse to find a crowd gathered around the building as it appears to be on fire. Racing inside, it quickly becomes clear that the fire is an illusion. However, on discovering Yargos two aides dead and the Infernal Incantation, the agents are set upon by a vicious erinyes devil. The wicked devil proves a difficult encounter for the agents, but they eventually defeat it and find the unconscious historian. Investigation of the two dead aides shows that one was shot by the erinyes devil, but the other was stabbed by a nearby coral hilted dagger. Yargos is unclear on what happened to his assistants, but implores the agents to locate the Infernal Incantations sister book, the Celestial Song, which will allow the Incantation to be resealed before it releases further devils. Despite their frustration at Yargos, the group agree and head to Gilltown in the Eastgate Quarter to meet with Ollysta Zadrian, the head of the Silver Crusade. According to Yargos, one of his aides took the Celestial Song to Ollysta to get the information to complete the ritual.
On route to Gilltown, the agents are blocked into an alleyway by four thugs wielding coral hilted blades. The thugs demand the Infernal Incantation, but the agents quickly overpower the brutes and demand to know who sent them, learning they were in the employ of someone called the Sea Witch, operating out of the smugglers tunnels beneath Gilltown. The heroes rush on to meet Ollysta, quickly explaining the situation to them. The paladin explains that she never received the book for Yargos aide, and the group suddenly realise that the historians aide may have been in league with the Sea Witch since they found the coral hilted dagger at the townhouse. Concluding that the Sea Witch likely now has the Celestial Song, Ollysta shares the ritual to seal the Infernal Incantation and a nearby gillmen merchant sells the agents a map of the tunnels. The Silver Crusade take Yargos into their care, leaving the agents free to pursue the stolen book.
As the agents progress into a quieter part of Gilltown, the air becomes unusually hot and a pentagram ignites itself into the floor before them. With only a dark warning on the wind, the agents find themselves ambushed by three bearded devils. Like the erinyes before, the bearded devils prove to be a challenging fight, but the agents emerge victorious. With the devils defeated, the agents are able to venture into the smugglers tunnels.
The tunnels seem completely abandoned, but echo with a chaotic chorus of celestial singing. As the heroes draw closer to the Sea Witches cavern, the singing becomes more chaotic and deafening. The four adventurers enter an antechamber that seems to be able to be filled with water, leading up to a suspended door and stairway thirty feet above them. Even in the painfully loud chamber, Albert is able to figure out the puzzle to flood the chamber to the correct level. As the chamber fills with water the agents are able to ascend the stairs to the now open doorway. In a grand chamber beyond they see the opened Celestial Song, guarded by Na-Kraka, the cecaelia sea witch.
Na-Kraka engages the group before they have chance to react, grabbing A’hymhu and dragging him down into the watery depths of the chamber the heroes just flooded. A brutal and chaotic combat ensues as A’hymhu and Lothaire try to battle the cecaelia underwater. A’hymhu is almost murdered by the witch, closely followed by Lothaire. Albert and Behnam manage to close the Celestial Song and seal the Infernal Incantation, before rejoining the fight. With the wizards and clerics help Na-Kraka is eventually defeated, A’hymhu only barely surviving the creatures merciless onslaught.
With the books recovered and the creature destroyed the agents return to the surface and report to Alexis. Congratulating them on their success, Alexis advises that the books will be dealt with accordingly, before dismissing them.