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

These dark dwarves – who said they are creatures of light? – are primarily associated with fire. It’s an interesting unit (I think everyone has seen the art for Heroes 7).

Well, personally, I didn’t say they were creatures of light :D
Yes, I’ve seen the art and the creature in Heroes 5, but I think the dwarven castle is good even without them, and besides, I would like to minimize the number of creatures created based on the same unit.