All castles in Heroes 3.

I was talking about the strength of the faction, not when playing against the computer, but when playing against another player! Even on XL difficulty, with two Inferno castles, it's necessary to build portals between them, as they are too expensive to build two! It's much easier to use simple scouts, arranging them in a chain, just like with any other castle. Or find a town portal in the guild. Playing against computers on any difficulty is not interesting.

Added 3 minutes later
In general, all of this needs to be tested in a duel. If anyone is willing to play, I'm ready to play with any castle against any castle of your choice.