Thinking back to the threads about the Adventure time AU where Finn is a vampire, and Marceline is the human kid.
>In this one, Finn and Marcy end up together in the end, making a new generation of Dampyr who grow into a vast underground society by the +1000 world
>With all of them being enternal life, but not eternal youth, their leadership is commanded by increasingly senile elders who draft ever more convoluted rulings
>Finn tried to keep his children organised, but left somewhere around the midway point.
>He does give the inventions for Dampyr civilization to be maintained indefinitely, including a regenerating source of red to feed off on.
>Maggie is part of the latest generation of Dampyr, and she gets exiled due to asking what's for breakfast.