Necropolis discussions.

"In my opinion, the only faction that can effectively counter Necropolis is Haven, because training is essentially cheating. Although it's expensive." IMHO, no faction in Heroes can completely dominate another (assuming the player is skilled and understands the strengths and weaknesses of the faction they are playing). Necropolis units are strong in numbers, as you correctly pointed out, but the real difference lies in the quantity of low-level creatures (skeletons, zombies). Necropolis has an absurd number of skeleton archers, but even when there are thousands of them, they aren't that effective. A decent opponent will have a sizable army by that point. Haven, Sylvan, and Magic factions have a good chance of obtaining the "Evasion" spell in the Guild of Mages, and with developed Light Magic, they can cast it on all their creatures on the battlefield, which reduces the damage taken from archers by 3.33 times (on Expert difficulty in Light Magic). Necropolis doesn't have Light Magic in its castle; they have their own advantages. But I'll reiterate my opinion: if a player knows how to play their favorite faction, they will use its strengths, and if they also prevent the opponent from exploiting their weaknesses, that's already half the battle won.