Inferno – “A fitting image for you” [Campaign 5, Mission 2]

He captured everything he could, but only collected three keys. The fourth one is nowhere to be found, even if he tries his best.
I'm playing on Steam, licensed version. Game version 1.4.0


Is this a bug?

Hello, I can't complete the quest. Eduardo constantly attacks me at the beginning of the mission, and I can't defeat him. My army is too small to win. I've started over 3 times, but I still can't win. He attacks me when I'm playing the first mission for Sandor, he attacks me right after I capture the castle.
Help me, how can I defeat him!