Get Morek or Luria to loot the place into the Stone Age. I doubt Sevastian can afford much militia. Or, as I said before, get a friendly priest/diplomat to work some magic. Preferably after you pay someone to stab Sevastian so he can't fix the place back up. Or just auto da fe him. There are still plenty of workable options. Fine him into oblivion. Ban all his supporters. Bribe/threaten/cajole all his lords into changing Duchies.
