Thank you Con, that is most interesting! I did remember reading something about how the Red Court Leeched from a tribe of gods, but couldn't remember where.
However, that actually only explains how the Lords of the Outer Night became gods/godlings. It doesn't explain the origins of the Court, as that passage implies the Red Court existed and were active and dangerous around that time - they had previously conquered the Mayans and then went after the Incas. Presumably they also conquered the Aztecs and the Olmecs and all the others.
So the original vampires of the Red Court, including the Thirteen who became the LoON and the Red King, where did they come from? Ariana seems to imply it was the Red King himself. If so, what was he originally? A man who became demonic, or a demon that emulated a man? Something of both I suspect.
I have a long standing theory that all Vampires come from the Outside. But have to change in order to stay. There is no supporting evidence for this, only speculation. But consider all Vampires are leeches - life energy or blood (life energy in physical form perhaps?) - and all of them prey exclusively on Mortals, specifically humans. Whilst some of them seem to be able to feed on other things (such as animals) they don't seem to prey in immortals much. But they can - as evidenced by the Paranet Papers. Vampires feature more heavily than any other supernatural race or threat, except maybe Faeries. I suspect this due to their significance in the series.
The Red Court are probably the oldest, although I suspect the Jade Court could give them a run for their money. Both Courts could well be several thousand years old, appearing perhaps 2000BC. If the Jade Court don't think the whole Qin (Chin) thing is going to work out (as Jim often says) which began approx. 200BC, they could be very old indeed as Xia dynasty (the first dynasty of the area that became known as China) begins around 2070BC.
So I suspect they appeared all around the same time: as humanity developed civilisation (around 3000BC or so). Whilst many cultures had been around at this point for some time in China, Egypt, Mesopotamia, India, Australia etc. Civilisation first seems to crop up around 3000BC approx. A significant event in human history, though the degree depends on whether Jim is including a Creation event in his timeline (we are dealing with Angels and Gods etc). Anyway, I suspect while plenty of supernatural things had been around (such as the Old Ones and Outsiders), some were just getting started. So the early Gods (who became the Old Gods) were probably around in various forms and names, and the survivors quite probably went into new cultures and adopted new masks (which became Mantles), as the Paranet Papers implies. The Fae probably were not around - there wasn't a hell of a lot going on in Ireland or Europe for that matter.
So the vampire creation starts around here. If they were merely hungry creatures from the Nevernever, drawn to humanity that might make sense. But I think some of corrupted humanity may well have sought out the Outsiders for power, and in order to sustain their terrible power and immortality they had to feed off the rest humankind. Outsiders hate humanity. Not just creation, although that is part of it, but they seem to not only want to obliterate everything but enjoy making mankind suffer. They like getting us to turn on each other and ourselves. Remember, the Outsiders were Inside once before and ruled the planet but did NOT destroy it. They tortured humanity first. Why? No idea. But I suspect this is why Vampires must feed.
Everything we know about Vampires tells us their very existence is an affront to Free Will. In order to become a Vampire, you must kill someone. In order to stay powerful and sane, you must continue to feed. The more you do the more you want to kill. But the act of becoming a full vampire is a Choice in most cases (BCV are the exception - but more on that soon). Reds turn their victims half-way, but the victim must kill someone for the full transformation. White Court are born as the offspring of a WCV and a mortal, but also must kill someone during their feed to become a full WCV. We know almost nothing about Jade, but if they are anything like the Chinese vampires, they also feed on life force (and I imagine a kill is necessary). They all seem to be able to mind-control mortals. WCV use sex and feeding to control their victims. Reds use some sort of eye-induced control, plus their highly narcotic saliva. BCVs use flat out mind control and can even push their power into a mortal human or animal and turn them into a nastier, rabid monster. Once turned, all vampires seem to have very little Choice left. Including self-determination of what they will be (this could be linked with Naming). WCV (maybe because they are relatively new, only showing up around 900BC) seemed to have developed traits that allow them to disguise effectively from mortals and get close, and as such are weaker than other vampires (unless they draw upon their limited reserves of power) but can cross thresholds. Reds seem to be slowed, but can push through (but leave a chunk of their power at the door). BCV cannot cross at all. So I think this all could point to the similarities with Outsiders.
I think Black Court Vampires are different for a few reasons. They are the newest having only been created 600 years ago, and come directly from something truly awful (Drakul). Drakul seems to be a hell of a lot stronger than the Red King and his Lords, or the White King (assuming Lord Raith is the original White King). Also though, the BCV turn their victims directly (their victims never have to Choose to kill to become a BCV). This might be something to do with their heavy association with Necromancy. Perhaps in order to turn a victim, you have to drain it dry and then bury it in it native soil (like in the myths) and then they are 'resurrected' no longer really the person they were before. But I think as Vlad Dracula botched the ritual of turning himself into the first Black Court Vampire, he was subsequently more vulnerable than the others too despite the massive strength he got. And he removed the Choice to become a BCV, it is made for you when you are their victim. Real question is why Dracula did it at all - considering he was Drakul's son, as a Scion he should have been more than strong enough already when he Chose. Perhaps he wanted more, perhaps he only Chose after he died. Either way, Drakul wasn't impressed with the result. Perhaps Drakul has been the one creating the vampires all this time, hence why he wasn't especially impressed with Dracula's poor attempt.
Anyway, back to the Reds. The original myth of Kulkulcan is that he is a boy that was born a snake and grew too big. Maybe that is similar to the Red King - perhaps he was the first mutant of his kind. And then he fed on the real Kulkulkan or whichever god. Or perhaps he made a deal with something hideous, or was possessed. Perhaps he was something horrible that entered the mortal plane.
The really interesting thing is of course, is what were the original gods? Wizards with pretending to be gods, perhaps with no restriction on Power? Perhaps they were another species that fed on the beliefs and worship of humans? Perhaps something else all together?
Of course, "Vampire" could just be a category like mammals or even animals, where the beings are all somewhat similar but their origins are completely different. Still though, the fact they are all Courts and have similar characteristics is intriguing and suggests a shared origin.
Great topic Ser Scot!