The weakest castle in Heroes of Might and Magic IV!

weak castles probably don't exist (just like monsters during construction). The balance in the 4th game is actually pretty good; almost everything depends on the player's skills + luck. It's just that most players aren't very inventive in terms of tactics/strategy, which is why stereotypes/patterns appear... But if I had to choose, I'd say Nature is the weakest, only because the Druid can sometimes be defeated in the first 1-2 turns, meaning summoning is a rather specific tactic; you might not even have time to summon anyone... but to say that it's "weaker"... you can't.