Outcast's Path

I’m saying it again, don’t rush to kill characters, whether they are mine guards, village guards, etc. They are all quest-related. You can always kill them later, but you won’t get the quest if they are already dead.

So, they gave me a quest to capture this mine...

+ It’s not clear how to build up an army if, in 20-25 days, this yellow guy will return again with an even stronger army and simply sweep away 3 incomplete reinforcements.

Has anyone completed it with a hero?

And regarding mobs, I only killed those that guarded resources or Sanctuaries. + I took Utopia – they gave me 2 rings with +2 HP and 2 identical amulets.

Added 5 minutes later
The only option I see is to get the mentor and level up the hero through education + mana attraction and the complete Wizard skill tree and fight with spells. At the moment, the demons leave 100 mana, and what should I do with it?

But then I will have to forget about building up the Castle, because the money will go to the mentor instead of buying resources + it’s not clear how to fight mobs with such a build.