Once upon a time... there was a succubus.
Evil creatures born from the sinful pleasure of sexual intercourse, corruption that emanates from their corrupted cores are their power source.
Years of studying kept the princess prepared for her plan, and this succubus that appeared out of thin air was when it all began.
The princess knew that this was a gift from the heavens, a sign of her fate, the ultimate gift that would take the ultimate cost, and it wouldn't be the princess that pays the weight.