The Servant Girl Is a Maxed-Out Saintess

A sealed saintess, reduced to a servant and blood bag, endures abuse until her power unlocks in a death match, igniting her revenge. With an ancient god's heir who shields her, they expose a traitor elder conspiring with the demon king. He burns his divine blood to seal the demon, losing his godhood. Justice served, they abandon their fate and retire to bamboo groves.