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

By the way, troglodytes could be made into an underground faction; they would be perfect for this role. And as a racial ability, you could simply rework the demon gates, as if additional troops are breaking through tunnels on the battlefield.

Troglodytes will be included, but I don't want to mess around with racial abilities and territories because it could lead to a lot of bugs, as it did with the old mod.

The underground city will have different monsters, like in Heroes 3, and they will be controlled by representatives of different races: dark elves, humans, maybe some kind of horned lich.
The ability will be the same – irresistible magic.