Forty Thousand in Gehenna, alternately 40,000 in Gehenna, is a 1983 science fiction novel by American writer C. J. Cherryh. It is set in her Alliance-Union universe between 2354 and 2658, and is one of the few works in that universe to portray the Union side; other exceptions include Cyteen (1988) and Regenesis (2009). The book was first published in a limited hardcover edition in 1983 by Phantasia Press, followed by a mainstream paperback release in 1984 by DAW Books. It was nominated for the Locus Award for Best Science Fiction Novel in 1984. Forty Thousand in Gehenna was reprinted in 2008 along with Cherryh's novel Merchanter's Luck (1982) in an omnibus volume entitled Alliance Space. Plot summary A group of 42,363 Union humans and azi are dispatched to set up a base on a very rare habitable planet named Gehenna II in the Zeta Reticuli system. Unknown to the settlers, their mission is designed to fail; they are deliberately abandoned in order to create long-term problems for the rival Alliance. The native calibans are first presented as annoying lizard-like creatures constantly moving earth to make incomprehensible patterns. The humans at first attempt to keep them outside a perimeter or to drive them away. In time, larger and larger calibans are seen, with differences in color, size, and a social structure (gray calibans are subservient to the larger brown calibans). It becomes clear that the creatures are capable of communication, at least at the level of symbology, and of developing empathic or possibly telepathic links to humans. Eventually a symbiosis develops, with some of the calibans pairing off with humans. Over a period of several generations and cut off from resupply, the colonists lapse into a primitive lifestyle. By necessity, the azi are allowed to raise families. The non-azi humans are in the minority from the beginning and over time, intermarry with the majority. An Alliance mission first seeks to intervene, then withdraws from direct contact, content to watch as two quasi-feudal, fundamentally opposed societies develop, while a third, smaller group called the "Weirds" becomes much more closely associated with the calibans, living with them rather than the other humans and becoming less comprehensible in the process. The novel follows several generations of descendants of one azi who establish different lines and rise to become the leaders of two rival cultures. Historical moments depict the decline of the colony, the