Alright, well I basically got done and came up with the Succubus/Incubus race and kingdom backstories 3 days before I realized what I had was final-draftish. But hey, it's good so I'll post my notes on their race first, then the kingdom.
---------------------------------------------------------
Race Notes:
Succubi need semen to remain healthy, and need it administered either in the mouth or vagina. (vagina bit wasn't in research, but decided to make it so)
Incubi are kinda the same where they'd need vagina sexual fluids and can get them into their bodies by consuming by mouth, or from vaginal sex where the fluids are absorbed by their penis.
In my research of Succubi, I came across this interesting line of "Religious traditions hold that repeated sexual activity with a succubus may result in deterioration of health or even death." and I'm deciding on keeping it for non succubi/incubi.
They need about 10 cubic centimeters of sexual fluids from the opposite sex a month to be healthy. They can die from poor nutrition within a week if fluid intake is low the month before, and little to none the month after.
They don't need to eat food, however eating food can help them live longer if mel nourished so they could live a little longer for a chance to get sexual fluids in the future. It could also be used as a little boost of energy, for things like getting up in the morning.
Succubi/Incubi have special eggs/sperm that usually only effects their race. It is extremely rare for a human to have an incubus's child, and for a succubus to be impregnated by a human. Other humanoid races aren't effected at all, and succubi/incubi don't go after non-humanoid races at all.
A child succubus/incubus usually "leaves the nest" by age 21 (looks 14(ratio is 3/2)) and don't need sexual fluids to survive till puberty, which is usually around this age.
They have tails, wings, and horns. They can use their magical powers to conceal their horns. They could do the same for their wings and tail, however don't need to since they can retract their wings and hide their tails in clothing most times. Most incubi don't have wings, and aren't suppose to, however some are born with a rare gene that allows them to grow wings.
The above note lead to this one later: Ages ago, the Succubi/Incubi only raped people for their sexual fluids, and only practiced consent through their own race. One day however, someone of the race got ahold of a book of magical spells, learned some of the spells to disguise themselves as different races, and figured out ways to get sex/sexual fluids that's easier and less of a hassle than rape. Because of this, they used the new techniques to seduce willing people and even used prostitution to get the nutrition they need. After having a child, they passed the spells along to their spouse and kids to help them out. Many generations later, the spells are known and used by many Succubi and Incubi, and thus the race raped way less, to about the same amount of rapes the human race does a year.
Most have high sex drives and most aren't sexually sensitive, so most don't feel much pleasure from sex, but their bodies make them crave it cause their bodies need the sexual fluids to survive.
And then there's this one where I'm not certain if I'll have it as a trait or not yet, where they're strongly resistant to STDs (when healthy?). So yeah, that one's a little iffy.
---------------------------------------------------
Kingdom Notes:
Long ago was mostly solitary creatures that stayed in families till child "leaves the nest"
A succubus/incubus wanted to help race thrive, so started a group (how?)* and started to learn farming and farmed food for mel nourished succubi/incubi.
(how?)*= maybe started a service from the farming and their idea(s)/efforts inspired others to contribute.
No real "Human to Succubus" trading ever went on, so no real allies to depend on.
And the actual storyline I thought up for the kingdom:
As the Succubi Kingdom formed, the residence felt like the "need" to rape was getting thinner and thinner, to which they were thinking about setting laws against it. However that lifestyle came to an end.
A powerful sorcerer named Tirek arrived one day and made a scene in the middle of the kingdom. He shouted about how a neighboring human village investigated a matter on why several people were getting mysteriously weaker and weaker as time passed. The one the village sent out to investigate found out that everyone with such conditions were having sex with prostitutes that were succubi and incubi in disguise. Assuming they came from the Succubi kingdom that recently formed a little ways from their village, they hired Tirek to put a stop to the prostitution deception. And so, in the middle of the kingdom, Tirek Conjured up a strong magical spell that stole all the magical ability from the residence of the kingdom. He started to leave when some of the inheritance figured out what had happened, and attacked Tirek, but were no match for Tirek's magical strength. With no magical abilities to disguise themselves, the whole kingdom's "only" way to get the fluids they need to survive were to rape like in old times, and the current queen made the difficult discussion to start kidnapping people to use as the kingdoms sex slaves.
------------------------------------------------------
So yeah, this will work nicely into the Succubi/Demon Clan war and how I plan on it resolving.