Incubus is a 1966 American horror film directed by Leslie Stevens. Filmed entirely in the constructed language Esperanto, the film stars William Shatner, shortly before he would begin his work on Star Trek. The film's cinematography was by Conrad Hall, who went on to win three Academy Awards for his work on the films Butch Cassidy and the Sundance Kid, American Beauty, and Road to Perdition.
The film is set in the village of Nomen Tuum (Latin, "your name"), which has a well that can heal the sick and make a person more beautiful. Because of the latter, many conceited or corrupt individuals come to the village for this cosmetic effect. The village has notoriety for its magical water, as well as being a ground for darkness and demons. Along the village, succubi entice the tainted souls who come to Nomen Tuum and lead them to their deaths in order to offer their souls to Hell/the God of Darkness. A prominent young succubus named Kia (Allyson Ames) loathes the routine of herding sinners to hell. Kia claims her powers are being wasted, and needs something/someone more stimulating as her prey. Her sister succubus, Amael (Eloise Hardt), warns Kia of the danger that a pure soul will bring: love. Kia persists anyway and attempts to find a clergyman to seduce into darkness. After watching their behaviour, however, she realizes these men are just as iniquitous and shrewd as her previous victims.