The Faceless race.

Level 1 - Shadow. Ability: After the end of the battle, 100% of the original number of shadows are restored. But only underground, where there is a shadow. And you can also add auxiliary beasts and monsters, like those worms and other monsters. As a result, it will turn out to be a kind of remake of the Dungeon faction from Heroes 3, but with a slightly different spirit and more diverse. And it is easy to make their storyline appearance - they are creatures of darkness - and it is nothing for them to create veils of darkness over their cities in order to remain unnoticed.