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

Now, instead of having the Winter Guard, we'll have Desert Orcs. Is that right?

Added 18 minutes later

Maybe, instead of summoning elementals, we could summon demons or shadows?

If we can change the list of summonable creatures, I suggest doing it like this:
Name: Summon Shadows

Creatures: Shadow (a regular unit with a black texture and effects), Forgotten Ones (a creature from the dungeon with darkened textures and the ability to disappear), Faceless Ones (I think it's clear), Shadow Guard (a rider on a lizard without the lizard, with black textures and tentacles instead of legs, like the Faceless Ones)

Name: Summon Demons :smile51:

Creatures: Cerberus (I think it's clear, but it needs to be made a 4-unit creature, for example, using a model from the 6th game), Sadist from the 6th game (we can use the Minotaur model), Devil's Servant (repaint the witches in red, give them a flaming axe, and make their eyes glow), Succubi (regular succubi, but completely burning)

Added 18 minutes later
And these artifacts instead of the Elemental Belt:

Shadows: Belt of Shadows

Demons: Fiery Belt