Necropanther

The reanimation trigger fires on every mutate, not just the first, and that single wording turns a routine enters-the-battlefield rebate into a repeatable engine. Stack another mutating spell over the same pile, or return a mutator and go again, and each event hands back another creature card from the graveyard. The mana-value-three-or-less clause is the restriction paying for the effect: it keeps the loop pointed at cheap value creatures (mana dorks, sacrifice fodder, hatebears, other small mutators) rather than acting as a general reanimation spell that bridges to fatties. That cap is the difference between an Orzhov engine piece and a black recursion tool wearing a white splash. Hardcast for its full cost, the 3/3 body carries the trigger but no way to fire it, which is the intended shape: the payoff arrives through the mutate cost, where every stack event trades a card for a body already sitting in the yard. It sits at the seam of black's recursion and card advantage, priced in white's structural discipline, the small-target cap keeping the engine from tipping over into a cheat. The Cat Nightmare typing and the over-or-under wrinkle of mutate are texture; the repeatable trigger is the reason to assemble a pile around it rather than simply cast it as a body.