An incubus is a Lilin-demon in male form who, according to mythological and legendary traditions, lies upon women in order to engage in sexual activity with them. Its female counterpart is a succubus. Salacious tales of incubi and succubi have been told for a large number of centuries in traditional societies, and Genesis 6:4 is a passage used to support the credibility of such stories. Some traditions hold that repeated sexual activity with an incubus or succubus might result in the deterioration of health, or even death.

Etymological, ancient and religious descriptions

The word incubus is derived from Late Latinincubo (a nightmare induced by such a demon); from incub(āre) (to lie upon). One of the earliest mentions of an incubus comes from Mesopotamia on the Sumerian King List, ca. 2400 BC, where the hero Gilgamesh's father is listed as Lilu. It is said that Lilu disturbs and seduces women in their sleep, while Lilitu, a female demon, appears to men in their erotic dreams. Two additional corresponding demons appear as well: Ardat lili, who visits men by night and begets ghostly children from them, and Irdu lili, who's known as a male counterpart to Ardat lili and visits women by night and begets from them. These demons were originally storm demons, but they eventually became regarded as night demons because of mistaken etymology. Written later but described as happening before the Sumerian King List was completed is the mention of the Nephilim: Christian tradition attributes the completion of the Biblical book of Genesis to the time of the sixteenth century BC, and in chapter 6, verse 4 describes fallen angels having sexual intercourse with human females just prior to the flood of Noah, traditionally held as happening in the 24th century BC.

Incubi were thought to be demons who had sexual relations with women, at times producing a child by the woman. Succubi, by contrast, were demons thought to have intercourse with men. Debate about the demons began early in the Christian tradition. St. Augustine touched on the topic in De Civitate Dei ("The City of God"). There were too a large number of alleged attacks by incubi to deny them. He stated, "There is additionally a quite general rumor. Many have verified it by their own experience and trustworthy persons have corroborated the experience others told, that sylvans and fauns, commonly called incubi, have often made wicked assaults upon women." Questions about the reproductive capabilities of the demons continued. Eight hundred years later, Thomas Aquinas lent himself to the ongoing discussion, stating, "Still, if a few are occasionally begotten from demons, it isn't from the seed of such demons, nor from their assumed bodies, but from the seed of men, taken for the purpose; as when the demon assumes first the form of a woman, and afterwards of a man; just so they take the seed of additional things for additional generating purposes." This view was additionally shared by King James and in his dissertation titled Dæmonologie he refutes the possibility for angelic entities to reproduce and instead offered a suggestion that a devil would carry out two methods of impregnating women: the first, to steal the sperm out of a dead man and deliver it into a woman. If a demon could extract the semen quickly, the transportation of the substance couldn't be instantly transported to a female host, causing it to go cold. This explains his view that Succubae and Incubi were the same demonic entity only to be described differently based on the sexes being conversed with. Being abused in such a way caused women at nunneries to be burned if they were found pregnant. The second method was the idea that a dead body can be possessed by a devil, causing it to rise and have sexual relations with others. This is similar to depictions of revenants or vampires and a spirit taking deceased corpse to cause a few mischief. It became generally accepted that incubi and succubi were the same demon, able to switch between male and female forms. A succubus would be able to sleep with a man and collect his sperm, and then transform into an incubus and use that seed on women. Even though sperm and egg came from humans originally, the spirits' offspring were often thought of as supernatural.

Some sources indicate that it might be identified by its unnaturally large or cold penis. Though a large number of tales claim that the incubus is bisexual, others indicate that it is strictly heterosexual and finds attacking a male victim either unpleasant or detrimental.

Incubi are at times said to be able to conceive children. The half-human offspring of such a union is at times referred to as a cambion. An incubus might pursue sexual relations with a woman in order to father a child, as in the legend of Merlin.

According to the Malleus Maleficarum, exorcism is one of the five ways to overcome the attacks of incubi, the others being SacramentalConfession, the Sign of the Cross (or recital of the Angelic Salutation), moving the afflicted to another location, and by excommunication of the attacking entity, "which is perhaps the same as exorcism." On the additional hand, the Franciscan friarLudovico Maria Sinistrari stated that incubi "do not obey exorcists, have no dread of exorcisms, show no reverence for holy things, at the approach of which they aren't in the least overawed."

Regional variations

There are a number of variations on the incubus theme around the world. The alp of Teutonic or German folklore is one of the better known. In Zanzibar, Popo Bawa primarily attacks men and generally behind closed doors. "The Trauco", according to the traditional mythology of the Chiloé Province of Chile, is a hideous deformed dwarf who lulls nubile young women and seduces them. The Trauco is said to be responsible for unwanted pregnancies, especially in unmarried women. Perhaps another variation of this conception is the "Tintín" in Ecuador, a dwarf who's fond of abundant haired women and seduces them at night by playing the guitar outside their windows; a myth that researchers believe was created throughout the Colonial period of time to explain pregnancies in women who never left their houses without a chaperone, quite likely covering incest or sexual abuse by one of the family's friends. In Hungary, a lidérc can be a Satanic lover that flies at night and appears as a fiery light (an ignis fatuus or will o' the wisp) or, in its more benign form as a featherless chicken.

In Brazil and the rainforests of the Amazon Basin, the Amazon River Dolphin (or boto) is believed to be a combination of siren and incubus, that shape-shifts into a quite charming and handsome man who seduces young women and takes them into the river. It is said to be responsible for disappearances and unwanted pregnancies, which metamorphoses back into a dolphin throughout the day. According to legend the boto always wears a hat to disguise the breathing hole at the top of its head.

The Southern African incubus demon is the Tokolosh. Chaste women place their beds upon bricks to deter the rather short fellows from attaining their sleeping forms. They additionally share the hole in the head detail and water dwelling habits of the Boto.

In Swedish folklore, there's the mara or mare, a spirit or goblin that rides on the chests of humans while they sleep, giving them bad dreams (or "nightmares"). Belief in the mare goes back to the Norse Ynglinga saga from the thirteenth century, but the belief is probably even older. The mare was likely inspired by sleep paralysis.

In Assam, a north-eastern province of India it is mostly known as "pori" (Assamese: পৰী, meaning "angel"). According to the mythology, Pori comes to a man at night in his dreams and attracts towards her. Gradually the victim's health deteriorates and in a few cases a tendency to commit suicide generates in him.

In Turkish culture, incubus is known as Karabasan. It is an evil being that descends upon a few sleepers at night. These beings are thought to be spirits or jinns. It can be seen or heard in the nightmare and a heavy weight is felt on the chest. Yet people can't wake up from that state. Some of the causes are sleeping without adequately covering the body (especially women) and eating in bed.

Scientific explanations

Victims might have been experiencing waking dreams or sleep paralysis. The phenomenon of sleep paralysis is well-established. During the fourth phase of sleep (the deepest stage, additionally known as REM sleep), motor centres in the brain are inhibited, producing paralysis. The reason for this is ultimately unknown but the most common explanation is that this prevents one from acting out one's dreams. Malfunctions of this process can either result in somnambulism (sleepwalking) or, conversely, sleep paralysis - where one remains partially or wholly paralysed for a short time after waking.

Additional to sleep paralysis is hypnagogia. In a near-dream state, it is common to experience auditory and visual hallucinations. Mostly these are forgotten upon fully waking or soon afterwards, in the same manner as dreams. Notwithstanding most people remember the phenomenon of hearing music or seeing things in near-sleep states at a few point in their lives. Typical examples include a feeling of being crushed or suffocated, electric "tingles" or "vibrations", imagined speech and additional noises, the imagined presence of a visible or invisible entity, and at times intense emotion: fear or euphoria and orgasmic feelings. These often appear quite real and vivid; especially auditory hallucinations of music which can be quite loud, indistinguishable from music being played in the same room. Humanoid and animal figures, often shadowy or blurry, are often present in hypnagogic hallucinations, more so than additional hallucinogenic states. This might be a relic of an ancient instinct to detect predatory animals.

The combination of sleep paralysis and hypnagogic hallucination could easily cause someone to believe that a "demon was holding them down". Nocturnal arousal etc. can be explained away by creatures causing otherwise guilt-producing behavior. Add to this the common phenomena of nocturnal arousal and nocturnal emission, and all the elements required to believe in an incubus are present.

On the additional hand, a few victims of incubi could well have been the victims of real sexual assault. Rapists might have attributed the rapes of sleeping women to demons in order to escape punishment. A friend or relative is at the top of the list in such cases and would be kept secret by the intervention of "spirits".