What about this idea for a specialization? After a battle, the hero "captures" part of the enemy army (essentially, he can replenish his army with a portion of the enemy creatures he killed). Although, it's quite similar to necromancy.
And if the opponent is just a hero, it's not very applicable.
Added 1 minute later
I would slightly correct the biography, it doesn't sound very good to say "carrying a LOT of enemy blood on his blade," but I haven't come up with anything better yet...
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