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

Uriel, I've said it a hundred times, you can't just take a model from Disciples and add it to Heroes 5; I mean, you can, but there won't be any animations.

The whole point is that we only need the models.
Then, instead of creating a creature from scratch, we can adapt an existing model, then recolor it and add alternate textures (and just add more effects, etc.).