actually this node
only portrays the modern
view of a succubus
--the one that was left in place mostly by *churches
* in the middle ages
by nature succubi are not evil!
a succubus is merely a female or female-ish spirit that seeks sex--or a relationship with any physical component--with mortals. (note: all of this applies as equally to the male incubus form).
a succubus is *not* a "race" of being, as are say fey, or sprites or whatever, but rather a *type*. succubi can be otherworld souls such as fey or elementals. they can be human souls who are currently in a limbo-state, not allowed to reincarnate yet or somehow trapped by some aspect in the world they left they can't bring themselves to let go of. they can be any kind of being at all. the only thing that defines a succubus is the desire of physical and almost always sexual human contact. these beings have come to the conclusion that being bodily with a human is the closest they can come to being fully human themselves.
for most, it is a desire to have a human soul, or for human souls, to "regain" their humanity. it is a hunger to comprehend the mortal world and partake of it as fully as they can. most have *no intent* of evil, only *need*. if it is a human soul, they are drawn to flesh that they knew in life, or that *reminds* them of someone they were close to. otherworld souls are drawn to humans, irregardless of their physical, but how truly *alive* they are in soul, and how psychically and spiritually attuned they are. they also often answer a call if a human is *looking* for a noncorporeal partner. (note, i do not recommend the average person attempt Summoning Demons For Sexual pourposes. -_- )
succubi are sometimes accused of being "soul-stealers", and something like this DOES happen sometimes, but again it's not as it looks. legend says every time a human has sex with a succubus/incubus, the being steals a little bit of the human's soul, and that the human becomes more and more addicted, wanting more, until their soul is completely owned by the predator. this is not fully true, but rather this is the case: sometimes a human will become completely *enamored* with their spirit-partner, *especially* if the succubus is an otherworld. most spirits are free from a lot of human constraints-- well for one they always have time they're not at work earning a living and often busy, they don't have "friends" to go out to the pub with in the same sense humans do, and succubi *tend*, once fairly involved, to be entirely exclusive so there's little risk of them leaving. additionally, spirits, human and non, in general have less of the darker human emotions such as rage and jealousy and such; a succubi's strongest feeling is *need*, so as long as you satisfy them, they are faithful and truly good to you. so humans often become fixated on these seemingly too good to be true partners, and slowly lose interest in what's "real". they often drift away from flesh friends, lose interest in their job and the outside world. but there is no soul-stealing here, rather the mortal chooses to *give* their life/soul.
now as to the issue of where the negative portrayal of demonwomen came from? the church, and society. during various times in history the church has gone on "sex is only OK in marriage/masturbation is bad/sexuality is unhealthy/divorce is a sin/etc etc etc" bents. because of course **we** are human, and not merely lowly animals of course we can control our hormones, right? the church didn't like to accept the fact that strong physical needs existed--of course no proper, god-fearing man would be animal enough to ever have a wet dream because *gasp* he had hormones. right? of course not. there *had* to be *some* explanation, and during periods where beliefs in spirits and devils and beings was still high, what better logic than "it must be a devilish being *tempting* these good men and trying to lead them to sin by having sex with them in their sleep." they took the *concept* of succubi/incubi from much older patterns of thought. (i do not know when the term was applied to these spirits, but the *idea* of them was around much longer than the name). so the church ran with this idea, and portrayed these beings in the sinful devil light they are commonly seen in today.
but actually...succubi have feelings too!