Succubus

Encyclopedia Entry:

A greater demon possessing extremely powerful abilities that lives in the demon realm, etc.  They are also called “inma.”  They appear in various places in search of human men even outside of the demon realm.  Some of them assume a human form and take up residence in human settlements.  The majority of the monsters that have changed into the form of a woman and begun feeding on human spirit energy have done so due to the influence of the demon lord, however, the succubi are a race that have always had the form a woman and fed on spirit energy, even ages ago.

In order to meet the desires of a wide variety of men, they range from having full, voluptuous bodies, to having bodies that stay like that of a child and never grow.  Despite the variations, all are beautifully lewd, arousing the desire of men.  Just as their appearances vary greatly, so too do their personalities, but every succubus has in common being extremely lustful and dedicated to the pursuit of pleasure.

They have powerful magic, but nearly all of it is used for seducing men.  Whenever they find a human man, they use charm spells, their gorgeous bodies, and various means to seduce him, and gain spirit energy through sex.  Every aspect of the succubus is designed to enable her to bewilder men.  Few, if any, would be able to elude the temptation, save for those men who possess truly remarkable willpower.  After gaining spirit energy, if they fancy a man, they’ll bring him back to their residence in the demon realm.

Also, they do attack human women as well.  In that case, they pour demonic energy into their partners through sex, and change them into succubi like themselves.  Humans who have just barely been changed into succubi are called lesser succubi.  Additionally, succubi can transform into men.

Through intercourse with a succubus, eventually a man will become full of demonic energy.  Such a man will have heightened sexual desire, and produce a high volume of energy to offer to the succubi.  They end up becoming beings that are extremely useful to the succubi.  Once this happens, they are no longer normal humans, but beings known as incubi whose very lives are fueled by the demonic energy gained through sex with succubi.  After becoming like this, one would be left with no choice other thanto continue having intercourse with them for the rest of his days.