Well, for the most powerful - it's the necros. I really don't understand what the argument is about, because how can you defeat such a freak who simply has an army twice as large as yours?

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And the dwarves are some kind of trash. They can't deal any damage; the fact that no one can deal damage to them either is no excuse!
Only their runes help (if the right ones drop; but if they're wrong - goodbye, shorties!)
It's just that taking their castle is difficult.