Walkthrough of the "Ambassador" scenario: https://www.youtube.com/watch?v=qwbEWxSg-WQ&list=PLGpNWhdMwySfH3y1lTq5mtu_gpaVdDs5l

Yeah, the AI where 60 archers kill 1 peasant is ridiculous; you won't get such an easy win with mods – it's impossible to pass even on veteran difficulty.

My question is, why is it necessary to attack Lorenzo's Castle?
I took Adrian with a ballista, and it became much easier, but when I approached the castle, I couldn't attack.

Added 4 minutes later
I sent archers to him – it worked!)

Added 31 minutes later
"Further on, there are sacred halls where foreigners are forbidden to pass."
This message now appears every turn for the blue player.