Jackal, Genius Geneticist

The copy trigger keys off an exact equality: the creature spell's mana value has to match this creature's current power, not fall within a range or clear a threshold. That single word, "equal," is the whole engine. It starts at power 1, so the first payoff is a one-drop copied off a one-drop, and every successful copy adds a +1/+1 counter that ratchets the target number up by one. The result is a climbing sequence: hit at one, and now you need a two-mana creature to hit again, then a three, and so on. Miss the number in either direction and the trigger simply does nothing, which makes deck construction a curve-matching puzzle rather than a goodstuff pile. The copies arrive as nonlegendary tokens, so the legend rule never chokes the loop even when you copy other legendary creatures, and trample gives the growing body a way to convert its counters into damage rather than stalling into a chump. What balances it is the discipline the equality demands: this punishes a top-heavy or bottom-heavy curve and rewards a deck built as a ladder, one creature at each rung to keep the power counter and the next castable spell moving in lockstep. The design turns a value engine into a sequencing exercise, where the reward scales with how precisely you can climb.