Warlord of the Pit (Outlanders Series #51) Book

The war to pull Earth and humanity back from the iron grip of slavery shifts against an inhuman enemy both calculating and unpredictable. For those with the knowledge and will to reclaim their planet, a blueprint for survival has emerged: to challenge the future, they must reckon with the chilling and immutable past.

Several baronies have disappeared, as if swallowed by the earth. Strange disturbances lead Kane and the others to a giant sinkhole in a remote and wild area of Mexico, where reality merges with an ancient culture of sorcery. Here, a beautiful, mysterious guerilla leader wages war against a terrifying army of demons spiriting humans into the subterranean netherworld. Joining the fight, the Cerberus rebels invade the cavernous chambers of a hidden world, and confront a self-styled warlord using pre Dark nuclear tech to rule the depths of the planet.