A subterranean power creates strange bedfellows for Jason and his friends in the epic next installment of He Who Fights with Monsters. Following the devastating attack on Yaresh, its people are left to pick up the pieces. The city lies in ruins, but its decimated defenders have more to deal with than just reconstruction. Jason's actions during the battle have brought unwelcome attention from allies and enemies alike. While the adventurers question his loyalty, the messengers question his very nature. Both have designs on Jason that he intends to thwart, but a danger comes to light that shifts everyone's agenda. Deep underground, a hidden civilization has survived by tapping into a long-buried power. That power's growing instability has become both a threat and an opportunity to the warring surface factions. Neither side can stop or claim the power alone, leading to an uneasy alliance with a reluctant Jason at the center. The adventurers, messengers, and Jason himself all have intentions for the power but little idea what awaits them below ground. There are more players involved than any of them realize, and soon, they will have greater problems than each other.