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leadership instead of education, don't take an attacking hero – take Runic Harmony.
Don't take a defensive hero, take Battle to the Last.
But this is just how I would do it.
But what about Armageddon's Blade? Is it really that bad?
16 is a normal value for magic. Plus, pyrokinesis works, so the damage should actually be multiplied by 2. And the Fire Lord reduces defense quite well, and elves have enough defense. Priests cast the Fire Sign.
By the way, I'm 100% sure that you play much better than your friend! You can tell him that directly. Because losing with Winghelm at level 25 – that takes skill!