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

I can't seem to "successfully" start this mission; the losses after the first battles don't pay off, leaving only 40-50 minotaurs for two heroes. Again, I've reread all the hints, but to my surprise, "it's not possible to easily capture castles"... The enemies cast fireballs and ice rings, and the computer has really "become smarter" in this mission... And by the way, on the 2nd or 3rd day, a strong hero arrives from the second castle, but the castle remains empty. The first castle also attacks on its own if it's not captured within 3 days. What should I sacrifice (assassins, furies, or minotaurs)? If in a Necropolis game, everything depends on the player, then in this one, it's the opposite; not only are the enemies higher level, but their armies are also one and a half times stronger...