Auto-translated
I have a plan for a leisurely playthrough with maximum hero leveling. First, I'll focus on Raillaga. If the most powerful demon appears after capturing the 6th castle, I'll try not to rush its capture. Out of five castles, 3-4 can be well-developed and provide enough troops so that two heroes can capture the last two cities simultaneously. After capturing the 5th city, I'll try to explore the entire territory and collect all the valuable resources. To protect the cities from raids, I can leave high-level heroes in the cities. I've already bought one hero of level 14.
If that doesn't work, I'll try to do it as Nightly Edelweiss suggests. I really don't want to give the enemy the cities that I've conquered with so much effort.