Fey'ri
The Fey'ri are a race of Planetouched native to the Forgotten Realms setting of Dungeons & Dragons.
In a nutshell, the fey'ri descend from fallen elven houses that turned to the forbidden art of demonology, for which they were imprisoned in what the other elves hoped would be an inescapable prison.
Long story short, it wasn't. But it held them for thousands of years, by which time generations of elf on succubus (and other demon) interbreeding had turned them into a unique form of tiefling.