...... Succubi/Incubi apparently don't have any variation in hair colour; their description either says: "Her/His hair is pumpkin." ,Or: "Her/His pumpkin hair is wavy." I've used to imagine Succubi with predominantly black hair; of course, this doesn't need to be the case, but why the colour pumpkin? Shouldn't there be at least some variation? (There is a great variation in skin colour, though!)
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Predominant hair/eye/skin colors are actually a vanilla feature, creatures inherit physical features from their mother and over a few centuries in worldgen certain bloodlines will outnumber the others because of sheer luck as other strains die out before they can reproduce. Succubi take that feature and run with it because so few succubi can actually find an incubus to get married to and so there's less mothers in worldgen for a set of genes to compete with.
Ui, didn't know that. I checked the succubi description in another game, and all their hair was moss green.
However, this brings me to one of my ideas concerning Succubi mythology: In classical Christian mythology, Succubi were 'genderfluid'. In female form they would have sex with men (while these were sleeping?) and extract their sperm, than they would change into a male form, Incubus, and sleep with woman. Since demons were not part of the creation or so, they could not reproduce on their own, but this way, they could even have children with each other, one in Incubus form could have impregnate one in Succubus form, their offspring would then be called Cambion.
(Check the Wikipedia articles on Succubus and Cambion for this.)
It would be awesome if something like this could be implement with a Succubus race in Dwarf Fortress. A Succubi fort would then consist of Succubis, Cambion (e.g. their children and young adults), and their male (!) human (elven, dwarven, goblin..) thralls. The male thralls would regularly be invited by a Succubus to a pleasure chamber (dedicated building or zone), and then a Succubi would 'satisfy their carnal desire'.
Once this has happened enough times, the Succubus would transform into an Incubus, and after 'he' has then impregnated another Succubus, it would transform back. Some male humans (elves, dwarves, goblins...? ) would deliberately move to a Succubi fort to live a life of unlimited carnal pleasure and become thralls, which of course would be a reason for their civilizations to declare war and siege the fort.
As far as the text-based part of the mod would be concerned, this should be possible without adding to the game sexual references that are more hardcore than those it already has; e.g. engraving descriptions that read: "This is an image of an image of a tentacle demon and a dwarf. The tentacle demon is performing a depraved act on the dwarf."
It would be important, though, to find words that are somehow less explicit that those commonly used for sex in modern English, to keep the style in which vanilla Dwarf Fortress describes these things. 'Carnal desire' should be ok, but it should be possible to find some more uncommon description, if necessary. I even looked up an extremely obscure word for 'sperm' just in case.
The other question is, of course, if this could be implemented technically with the game as it currently is. Would it be possible to have succubus-'caste', that transforms into an incubus-'caste' after performing the job "satisfy carnal desires" at the pleasure chamber at certain amount of times? Having a small chance (ca. 5%) of the succubus performing the 'job' successfully transforming into an incubus would also work.
Can 'thralls' from other sentient species be added to a fort, or would this require the tavern update, as I've read somewhere in this thread? Probably a Succubi fort could import male thralls as pets?
Anyway, what do you think of this idea? It would not only bring the DF-mod-Succubi closer to their original mythology and at some 'spice' to the gameplay, it should also fix the trait inbreeding issue.