“Heroes of Might and Magic V: Tribes of the East”

I don't use the auto-battle feature; I only play on the highest difficulty level.
It only works if you stop them and get 900 Cyclops from the second fighter; otherwise, it's impossible. But after that, you don't need any more battles; you emerge on the surface and go to destroy the main castle.
Thanks for the safe spot, but I've already played this map, slowing down the enemy fighters at the castles. I'm just very interested in how you can defeat this castle with the forces you're given initially.