The most challenging maps for you.

The Tower is a whole different story; the Castle is just too expensive, you'll struggle on Impossible!) I haven't played this scenario, but I can play it if needed.;)

Yes, I just asked. So we have something to discuss in general:)
Impossible is exactly the level that is interesting to play. It translates to "impossible." But when you play it, it turns out how easy it was to play.:) But first, you need to think and try:)

Have you played Heroes 2? There's a scenario there called "Pyramid," which is difficult. You have to measure every move with a ruler:) And in Heroes 3, there's a scenario called "Titan's Winters" or something like that. On the 1st island, there are 3 Titan Castles and 1 Castle with hippos, on the 2nd island, there are 3 Dungeon Fortresses, and on the 3rd island, there are 4 Knight Fortresses? It's also a difficult scenario, and you play as Titans. I also played it on Impossible. But for some reason, the most difficult and interesting scenario is "Champions of Gel," I recommend playing it. IMHO