The incubus was a demon figure closely associated with the vampire. The incubus was known for its habit of invading a woman’s bedroom at night, lying on top of her so that its weight was quite evident on her chest, and forcing her to have sex. The succubus, the female counterpart of the incubus, attacked men in the same way. The experience of the incubus/succubus attack varied from extreme pleasure to absolute terror. It was, as psychotherapist Ernest Jones noted, the same spectrum of experiences described in modern literature between the erotic dream and the nightmare. The incubus/succubus resembled a vampire in that it attacked people at night while they slept. It often attacked a person night after night, like the vampire of the Gypsies, leaving its victim exhausted. However, it differed from the vampire in that it neither sucked blood nor stole the life energy.
The incubus seemed to have originated in the ancient practice of incubation, where a person went to the temple of a deity and slept there overnight. During the course of the evening, the person would have contact with the deity. Often that contact involved sexual intercourse, either in a dream or with one of the very human representatives of the deity. This practice was at the root of several religious practices, including temple prostitution. The most successful incubation religion was connected with Aesculapius, a healing god who specialized in, among other things, curing sterility. Christianity, which equated the Pagan deities with devilish demons, viewed the practice of intercourse with the deity as a form of demonic activity.
Through the centuries, two main opinions on the origin of incubi and succubi competed with each other. Some saw them as dreams, figments of the fantasy life of the person who experienced their visitations. Others argued for the objective existence of the demons, contending that they were instruments of the devil. By the fifteenth century, church leaders, especially those connected with the Inquisition, favored the latter explanation and tied the demonic activity of incubi and succubi to witchcraft. The great instrument of the witchhunters, Malleus Maleficarum (Witches Hammer), assumed that all witches willingly submitted to incubi.
The objective existence of the incubus/succubus was supported by Thomas Aquinas in the thirteenth century; he argued that children could even be conceived through the intercourse of a woman with an incubus. He believed that a demon could change form and appear as a succubus for a man and an incubus for a woman. Some thinkers argued that succubi collected male semen then, in the form of an incubus, deposit it in a female. Nuns seemed a particular target of incubi, as demons seemed to delight in pestering those who strove to live the holy life. The idea of the objective existence of incubi and succubi held sway until the seventeenth century, when a trend toward a more subjective understanding became noticeable.
Ernest Jones, a Freudian psychologist, tied the incubus/succubus and the vampire together as two expressions of repressed sexual feelings. The vampire was seen as the more intense of the two. Because of the similarities of vampires and incubi/succubi, various forms of the latter often appear on lists of different vampires around the world such as the follets (French), duendes (Spanish), alpes (German), and folletti (Italian). Closely related to the incubus was the mare (Old Teutonic), mara (Scandinavian) or mora (Slavic), a demon of the nightmare.
Jan L. Perkowski noted that stories of the Slavic vampire also included elements of what appeared to be the mora. He considered these as vampire accounts that had experienced demon contamination. He carefully distinguished the vampire (an enlivened corpse) and the mora (a spherical shaped spirit), and he criticized vampirologists such as Montague Summers, Dudley Wright, and Gabriel Ronay for confusing the two. He also criticized Jones on much the same ground. While acknowledging that the vampire and mora shared a like mode of attack and generally attacked the same kind of victim (someone asleep), the vampire phenomenon was to be distinguished in that it centered on the corpse while the mora phenomenon had no such objective reference and was centered entirely upon the victim who survived the demon’s attack.
The incubus and succubus have been the subject of a variety of movies that span a wide spectrum of emphasis on the close relationship of these demons to the vampire. Between 1965 and 2005, there were six feature movies simply entitled Incubus, while in about the same time frame there more than a dozen named Succubus or a minor variation—Succubus: The Motion Picture (1999) or Succubus the Demon (2006). The film Incubus (1965) starring William Shatner is distinguished as being the only movie with all dialogue in the artificial language Esperanto.