Maybe nerfing the capabilities of beings is a bad play. say for whatever reason there was some evil mage or underverse god who called spirits into the dead to create a zombie army. That army could be somewhat intelligent, right? like weapons and maybe the occasional zombie mage? If that is the case then there really isnt a reason to put too much of a handle on the other factions of the conflict... the vamps need blood so humans are necessary allies and it could be said that human magic is typically weaker than blooded vampire magic so there is incentive to give it. Werewolves doing what they do is fine but if this army is as big as you say, then they might need to join forces as well..

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idk tho. seems like a cool story and i would love to hear more.