A succubus/incubus appears almost entirely human, and it's very difficult to identify their supernatural true nature; they seem to live and age like humans do, and to be able to survive on a normal human diet. Even vampires seem to be unable to differentiate incubi/succubi from humans. However, like other supernatural creatures, incubi/succubi can see and hear ghosts.
A succubus/incubus unconsciously exert a psychic or magical influence over people of the opposite gender; anyone of the opposite gender whom an incubus/succubus touches will experience a constant and almost uncontrollable sexual attraction towards them, which will only wear off once the person is no longer near the incubus/succubus (although the spell does indeed wear off very fast once they're apart). Incubi/succubi's seductive spell affects not only humans, but also vampires and werewolves. It is unknown whether or not ghosts would be affected.
When a succubus/incubus has sex with a mortal, the mortal will die either during sex or shortly afterward. According to Dominic Rook's leaked emails, the victim dies seemingly from natural causes such as a stroke or heart attack, making it very difficult to tell that an incubus/succubus is responsible. Sex with an incubus/succubus would be fatal to humans and werewolves, but vampires can survive sex with an incubus/succubus due to their undead state. This is all under the assumption that the succubus/incubus is not in love with whoever/whatever they chose to have intercourse with. Nobody knows for certain what happens when a succubus/incubus is in love but we do know that the partner they are in love with will not die during nor after sex.
As succubi/incubi are raised among humans, they may never discover that their aren't human. However, it was shown with Yvonne Bradshaw that if and when a succubus/incubus learns the truth about what they are and why the opposite gender finds them irresistible, they're at risk of feeling rejected and unable to form genuine meaningful relationships, which can in turn allow their demonic half to become dominant, leading them to seduce and kill people in their bitterness.
The only known succubus is Yvonne Bradshaw. According to the leaked Rook emails, besides her there is another woman and a man whom the Department of Domestic Defence suspect of possibly being a succubus and incubus respectively.
- Though only a succubus has ever appeared in Being Human, the Rookileaks confirm that incubi are the male equivalent of succubi and do indeed have the same abilities.
- Some fans have suggested that succubi may be classified as Type 5.
- It is unknown how common or rare succubi are. They are most likely very rare like zombies, because very few individuals in proportion to vampires, werewolves and ghosts have been known in the series.