Which castle is the most difficult?

Lider1, but what makes the AI so dumb?) It seems to play quite well, bringing in a powerful army.
Can you provide some evidence?

Of course, I can.
I'm attaching an archive now: it contains an autosave and a save file.
The autosave is from before the battle with the AI.
The save file is from after the battle with the AI.
It's a clear example of the AI's idiocy, where blue simply throws itself against the wall, and the battle ends up being very long (in the end, it's just finished off with magic arrows and towers firing at a strike force of 200+ Royal Naga).

All you have to do is end your turn, and blue will attack. Changing anything with artifacts is pointless, but you can buy a transport to allow for infinite firing. More experienced players will probably want to attack blue themselves.... although, in reality, there's not much for experienced players to do there.

P.S. Don't attack me now, saying that the map should have been much more explored and that there should be almost nothing left of the AI, considering that at least 3 heroes with good artifacts and decent armies are just standing around doing nothing, while only one is running around with all the troops...
This allowed the AI to develop for a little longer than it should have. The game is being played on Duke difficulty, although on this map, you could easily play on King difficulty, and there's no point in taking anything below Queen, as there are plenty of resources anyway...
Here's an example of how the AI is not intelligence, but an idiot, whether it's on Duke, Queen, or King difficulty, and here's an example of the AI's stupid behavior in battle. A human playing as blue would never lose in that situation