Ok, I am in a standard 5E Curse of Strahd campaign. The DM is interested in taking the campaign beyond 10th but wants my character, a Vengeance Paladin to become a dark lord by the end of the Curse of Strahd campaign. And wants my character to then become a NPC "big bad" for at least part of the levels beyond 10th. We are looking for a big way for my PC to become the villain. Looking for a really compelling reason that the party and my character would become strongly opposed - after the CoS module ends.
Any interesting suggestions or ideas?
PS - Are there rules anywhere on how one becomes a darklord?