I reworked everything, and saw that the map layout was a complete mess. The heroes each brought 1 stack, and there were exactly 0 golems.
I dug up a hero with a log and a ballista, and started shooting everyone. By turn 123, I had gathered 40 demons and 16 ducks from the chests, upgraded them, and started regenerating 90 mana with great stats and oil, but the opponent surrendered because they couldn't break through my defenses.
Thanks for the game.
Skype: vilco_O