Hello!
I have the same problem. I don't know how to avoid killing the Orc at the beginning because it's impossible to progress further on the map otherwise.
I eliminated everyone, and only Kasim remains. The towers for the bridge are not active. What should I do? The talisman I took from the Shantari in the lower right corner of the map has disappeared from my inventory. Maybe that's the issue. But I have no idea where it went; it's some kind of bug.
Thank you for any help!
Perhaps it's better to replay the map; it will be easier the second time!
I didn't kill the Orc... I'm a good guy!
And I didn't kill the sorceress... some Orc killed her, maybe even Djenko himself; I don't remember anymore!

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Неудачное планирование ведёт к неудаче ...
NCF - мод, добавляющий дополнительных существ в HeroesV 3.1