Since I'm sure this thread is clearly for the creation of cum settings, here's something related to two powerful fetishes, interacial enemy rape, and human semen cattle.
>Demons are the native sapients of the Netherworld. During the cataclysm known as "The Tangling", the Netherworld, Heaven and Earth ended up overlapping with each other. Heaven and Earth were able to survive easily, but the Netherworld suffers and is slowly being absorbed into Earth.
>Demons can enter into earth through places on earth that have consumed the Netherworld more strongly than anywhere else known as Demon's Gates. They can also be summoned by weaker demons (more on that later). Passing through via Demon's Gates is the vastly preferred method.
>The Tangling nearly destroyed demon reproduction, they initially believed that it had rendered them sterile. However, it wasn't long until they found that it wasn't the case (due to a demon warrior raping a male captive), and instead, demons are unable to breed with each other. Instead, they have to breed with the humans and elves of Earth, only ever producing full demons.
>Demons that become too powerful end up victims of their own success, they can only enter Earth via summoning. Even then, Demons summoned to Earth will leave something behind, ending up feral, animalistic and needing the direction of the weaker demon summoning them. While it varies from demon to demon, a summoned demon might have their magical or physical abilities cannibalize the other, resulting in a lean towards the other and even a wildly different form when summoned. This has created a misconception on Earth of there being different breeds of demon but they are all actually the same breed.