We've seen characters like England attempt to summon demons and other dark forces to cast curses and the like, and do black magic, or perhaps to try to persuade the dark entities not to do something. The forces of darkness can grant many favors and give those who petition them a great deal of power, but it doesn't come cheap. Demons may occasionally be affable, but they aren't nice. They feed on suffering and negative emotions.

So, I'd like to see magical nations making bargains with dark forces/demons, and paying with sexual services, however anon wishes. Tentacle sex/rape, dubcon, noncon, sex with eldritch abhominations, oviposition, forcing the character to break taboos, or seemingly break them, taking the form of their worst enemy (or unrequited crush to emotionally torture them). Feel free to go wild, as long as it isn't guro. I'm looking for erotic horror.

Bonus: The bigger the favor, the greater the payment required.
Bonus 2: It isn't a price if it's something that's easy for the character. They might physically enjoy themselves, but it's still disturbing for them.

No England/Canada, please, but any other pairingd anon wishes to include are welcome.

(I hope this makes sense and I didn't offend anyone.)