In folklore traced back to medieval legend, a succubus (plural succubi) is a female demon appearing in dreams who takes the form of a human woman in order to seduce men, usually through sexual intercourse. Repeated intercourse with a succubus may result in the deterioration of health or even death. Much more info in the link.
"If I were going to describe the perfect contraceptive, it would go something like this: no babies, no latex, no daily pill to remember, no hormones to interfere with mood or sex drive, no negative health effects whatsoever, and 100% effectiveness. The funny thing is, something like that currently exists." And it's for MEN! Bring it!