Which castle is the most difficult?

I don't like the Swamp – it's clearly not a city for long-term development. First, let's look at the advantages: a building that increases the defense of any hero visiting the Fortress; a double-width moat; Hydras inflict losses by attacking surrounding troops, hitting all surrounding units simultaneously; Wyverns replenish on the map, and the unit can be quite numerous; improved Gorgons, thanks to their deadly gaze, can effectively attack high-level enemy monsters; Basilisks can freeze the enemy for three rounds; Dragonflies are fast, remove enhancing magic from the enemy, inflict Weakness, and ensure the first turn for using magic until improved 7th-level units appear in the game. But in this city, the focus is on defense, weak archers, poor magic (limited to the third level), no "interesting" heroes, and the Hydra significantly slows down movement. The main army is slow, it is easily destroyed on the approaches through mass slowing and blinding, the fast snakes die quickly, and a lot of rare mercury is needed. Well, for a quick game, you can certainly find options, but they don't appeal to me for a more enjoyable experience; I don't know, maybe I just didn't like them since the time I played through the campaigns, and I have a lasting dislike for them.