RTF is a global modification that replaces all towns in the game.

On what basis did you form this opinion? How do you know how the NPC thinks? The only way to test this is to play the game.[

I'm playing on Hero difficulty with a friend, I installed a mod that increases the difficulty of neutral creatures, and Eva (because I can't update to 3.1 without it), and a minor mod that swaps the building locations for Inferno and adds a few new ones. In the late game, the demons barely had any army, and their castle was only half built. In any case, I think it's worth increasing their intelligence; they are already too weak, and with these changes, the NPC from the castle won't be able to field an army for a couple of months.