Fortress of Lost Worlds

In the fourth audiobook of the GONJI series, itinerant halfbreed samurai Gonji Sabatake falls into the hands of the Inquisition, as he and his comrades, human and supernatural, probe the mystery of a vast series of concentric worlds—a system of which our own Earth is but one. Oppressed by civil, military and religious powers alike, they are further stalked by a band of undead assassins, as they seek out an amazing other-worldly fortress in the Sahara Desert.