Succubi (the plural of succubus) are female demons that come to men at night and have sex with them.  Unfortunately, they don't actually exist.  Supposedly, it's bad for your soul or something.  My succubi are much more terrifying, at least to most men.  They possess mortal women, offer men a blowjob, and then, just as he's ready to come, bite his penis off and eat it.  The weird tattoos are the mark of the demon, but the weird-looking eyes and sharp teeth don't appear until they are ready to attack.  Be careful out there, you never know who might be one of them.