Uninvited guests.

Krusso, try playing as Haven (hero - Rupert). Considering his 2 specializations, your chances of winning will increase significantly + with this hero, the scroll: Portal to Town works.
And the witches' coven is located not far from the entrance to the dungeon.

I tried Rupert as a Warrior. Well, that's just ridiculous! Absolutely useless race, in my opinion, with its counterattack; on this map, the specialization is useless. What second specialization are you talking about? The ballista, yes, 3 shots are cool! The first demon won on the 3rd week; he has upgraded machines that immediately destroyed the gates, and his ballista buried half of my army; that's what I call a specialization!)))) I lasted longer even playing as Dwarves. When I played as Barbarians, there were no attacks at all; they didn't even dare.