Dig underground tunnels, build rooms and attract creatures at your service, then use your army to annihilate your enemies. Each room has a different use and can attract a specific type of creature, so it's up to you to build the best hive possible. You can even build traps or research new spells to improve your defense capabilities.
This is a phenomenal realization of all the fun of Dungeon Keeper. I expected it to be a buggy experience lightly touching on DK elements, but instead found a mod that recreates the game with a starcraft feel. 10/10.