The weakest castle in Heroes of Might and Magic IV!

Everyone has their drawbacks. You need to know how to work around them effectively. First and foremost, you need to be able to play on the contradictions between opposing factions.

Chaos has a magic surge that reduces the mana cost of spells by half.

Yes, but it would be great if there weren't one BUT. The magic surge reduces the cost of using spells for all heroes and creatures, not just your own, but also your opponent's. That doesn't seem very good. Although, in the absence of anything else, it's still not bad.