Question: "What is a succubus? What is an incubus?"
Answer: According to medieval folklore, a succubus is a demon that takes the form of a woman in order to have intercourse with a man in his dreams. The name comes from Old Latin, and means “to lie under.” In Islamic superstition, there is a similar demon called the qarinah or karina, and in ancient Middle Eastern cultures Lilith was the night demon's name. Whichever name is used, the essential qualities are the same: a demon who tempts men sexually at night and who tries to kill infants at birth.
There are two biblical passages that may refer directly to this kind of demon. One of the Dead Sea Scrolls (4Q184) depicts a being called “the seductress” who has horns and wings and a multitude of sins in her wings. This being tempts men into sin and ultimately drags them into the Pit. The passage is quite similar to Proverbs 2:18-19, which describes the dangers of the seductress or “strange woman.” In describing the results of God's judgment on Edom, Isaiah 34:14 (KJV) says, “the screech owl also shall rest there, and find for herself a place of rest.” The American Standard Version translates “lilith” as night demon or monster, and the Revised Standard Version uses the name “Lilith.” Some commentators have proposed that primitive cultures heard the cries of nocturnal animals and attributed them to demons because they had no knowledge of those animals.
Are succubi real? If we grant any credence to the widespread beliefs of ancient cultures, the answer would have to be yes. If we confine our search to biblical writing, the answer becomes more difficult. To be sure, the name has been associated with a demonic presence for several thousand years and fits in that context in the Bible. It is also certain that the Bible deals with demons as very real, very powerful beings which have dealings with mankind. Second Peter 2:4 speaks of angels who sinned and were cast down to hell in judgment. Jude 6 (KJV) likewise speaks of angels who “kept not their first estate,” and are awaiting the last judgment. Jesus cast demons out of people, as did His disciples. Whether or not we accept the idea of sexual tempters, there is no doubt that demons themselves are real.
The male counterpart of the succubus is the incubus, from the Latin incubo for "nightmare." An incubus was supposedly a male demon who would lie with sleeping human women in order to have sexual intercourse with them. Incubi were thought to be able to father children, and the half-human offspring of an incubus was called a “cambion.” Merlin, the legendary wizard from the King Arthur legends, was supposedly sired by an incubus, from whom he received his supernatural powers and abilities. Both succubi and incubi were the products of medieval superstitions and were most likely efforts to explain the natural phenomena that occur during sleep—nightmares, sexual dreams, sleep paralysis and night terrors. They are also thought to have been efforts to explain away nighttime rapes and other assaults on women by friends, relatives and even the clergy. It would have been easier to attribute such attacks to the supernatural than to admit they came from some person in a position of trust.
As Christians, we are warned against worshiping demons (Leviticus 17:7), and even their names should be forgotten (Zechariah 13:2). Some people study demons thinking that will help them carry on spiritual warfare. All we really need to know about the enemy is this: “Every spirit that does not confess that Jesus Christ has come in the flesh is not of God” (1 John 4:3, NKJV). Our focus should be on learning more about the One who “has delivered us from the power of darkness and conveyed us into the kingdom of the Son of His love, in whom we have redemption through His blood, the forgiveness of sins” (Colossians 1:13-14, NKJV). When we hide God's Word in our hearts, it keeps us from sinning against Him (Psalm 119:11) and gives us the weaponry to fight off any attack of Satan or his demons (Ephesians 6:17).