Warlock – “Cultist” [Campaign 4, Mission 3]

I'll try to recall. I didn't try to hold all the castles; they took the "second" one, but I recaptured it. I didn't give up the northern ones to anyone, and they also took the central one, which I recaptured as the second to last. I gathered an army from all the castles at the bend in the river. I rarely took troops from the "first" castle; closer to the end, I moved everything there. From the last castle (behind the garrison), I constantly repelled small sorties, and in the end, I captured it without any problems. As mentioned above, buying enemy heroes is also a good strategy.