Father of the Fairies

Immortality. Some see it as a blessing; others a curse. For Percy, its a bit of both. At least Mavis's brats aren't boring. Immortal!Percy OP!Percy. This is a reattempt at the crossover I tried ages ago, but also entirely different than that one. It's (as you guessed) highly self-indulgent and I'm really making this one up as I go along.