Might of the Old Ways
The pump spell is one of green's oldest tools, and the reward clause here bolts a cantrip onto it without inflating the base rate. The floor is exactly what a two-mana trick has always been: pay for a +2/+2 and nothing more, honest and forgettable. The ceiling is the coven clause, which asks for a board that already looks a certain way: a spread of bodies with distinct power values, the kind of diversity a token-and-anthem deck rarely produces but a curve of differently-sized creatures makes on its own. Clear that bar and the trick replaces itself, which changes how it plays at instant speed. You can hold it up as a bluff, cast it on an attack that already looks lethal, and still not lose the card. Fail to meet the requirement and it reverts to the bare pump. That contingency is the whole design lever. Most cantrip tricks bury the draw behind a narrow trigger tied to the spell itself; this one gates it on a board state you assemble deliberately, rewarding varied stat lines over a board of copies. It nudges deckbuilding in a specific direction (a range of power values rather than duplicates of the same body) and pays a card for having done so at the exact moment you were going to spend mana on combat anyway.

