Hect

Unless you're going for the gaiden (25 turns), take it very slow. Wait out the siege tomes and, if possible, lure out enemies 1-2 at a time.

That games balancing is awful in general lol

The difficulty spike was horrifying. That said, for the chapter, you'll want to rush it a bit in the first few turns, so you can stop the only thief reinforcement coming from the bottom right of the map. After that, you can crawl through the map at your leisure.

(Yes, I beat the chapter.)