The Saint is a demon king

There exists five specific souls who have a unique ability that allows them to have a second chance at life after death, they are known as mystics. Each mystic has their own unique ability that gives them another chance at life.

The demon king Vindicta has suffered many atrocities during his life especially towards the end and as he died the Demon race could no longer sustain itself and would go extinct. However he is given another chance of life as a saint however he still harbours hate for all the other species and has goals he needs to acomplish. How willl he accomplish his goals with other mystics lurking around with knowledge unique to them and how would he kill them.

Warning: This will have implications to rape ( not from the main character)
Author note: The protagonist is a villain but he has his own goals and motivation and so not every chapter will have him doing some horrendous stuff