Oboro Envoy

The Moonfolk bounce mechanic gets repurposed here from tempo to combat trick: returning a land becomes the fuel for shrinking an attacker, and the size of the shrink scales with how much you're holding. That coupling is the whole logic of the design. A full grip means a sizable -X/-0, but the activation costs you a land each time, so the ceiling on its power is also the floor on your development. Hold cards to make the ability hit hard and you're stranding tempo in your hand; spend cards and the effect withers. It blunts attackers rather than killing them (-X/-0 leaves toughness intact), so it answers a single beater for a turn instead of clearing the board, and a fresh-cast creature with an empty hand behind it does nothing. The 1/3 flyer behind it is a sensible holder of the ground while you decide whether the activation is worth the land. What balances it is that no single use ends a threat: it's a repeatable stall, throttled by both the generic mana and the land-to-hand tax, asking you to sequence your draws around when a defensive blunt is worth more than playing the card you'd otherwise return.