I see that you're giving Antimatter a more... interesting target based on the mechanic.
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You should probably name the ability something, but then again, the names for Gnome Gemfinders/Damselflies/Brimstone Eaters' quanta generation abilities are simply based off the element (Earth - Air - Fire - etc.). ^^;
Seeing as this card requires either Antimatter or several buffing spells (Blessing, Chaos Power (preferred due to it being mono), etc.) in order for the creature to be a real nasty attacker, I like the concept that it automatically triggers the ability even against shields, but I don't necessarily think it should heal for that much. Would it be more logical for the horse to simply generate
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quanta per turn (and lower the -negative attack value to -1 or something), so that it contrasts with the 'rainbow-quanta' gathering skills/synergies of Nova and Fallen Druid/Mutation?