With its angled orbit slicing through the plane of the solar system, many astronomers believe Apostae is not native to the Pact Worlds system at all — that it is, in fact, a derelict generation ship of extrasolar origin. Beneath the barren, airless surface lies a vast interior of artificial corridors, sealed chambers, and ancient alien technology built by the vanished ilee, a race now known only from skeletal remains and cryptic inscriptions. The drow who now control the world claim to have fled Golarion before or during the Gap, guided by demons to this hollow world. House Zeizerer holds the most power among the competing noble houses, which ruthlessly vie for control of newly discovered passages and technology vaults. Orcs and half-orcs, brought as slaves, occupy a permanent second-class status, performing dangerous exploration and manual labor. Two particular mysteries drive Apostae's politics: the Armory — a legendary cache of ilee weapons rumored to be planet-destroyingly powerful — and the Chamber of Life, believed to hold the secret of what happened to the ilee themselves. The surface settlement of Nightarch is named for a massive alien arch covered in undeciphered markings that occasionally generates random portals to unknown locations, a phenomenon the drow study obsessively but cannot replicate.