Nimbus Swimmer

The body that lands on the table is whatever you can afford to pour into it: a 0/0 base that exists only as a holster for the X, so every counter you buy translates directly into a flying brawler with no rounding error. The split-cost design is the wrinkle. The green-blue requirement is fixed and the scaling rides on top, which means the floor here is steeper than on a single-pip X spell: small early casts demand both colors for a body that barely justifies the click. Where the design pays you back is the ceiling, where two open colors fund a finisher that hits the air. Evasion is what separates this from the other X-fueled fatties: a big ground creature parked on a stalled board is a wall, but the same investment with wings becomes a clock, a haymaker that closes games it was never holding the ground in. It is the rare X creature that wants to be both a midgame play and a late-game bomb without changing what it is, and because the size arrives as +1/+1 counters rather than a printed boost, the investment stays live after it resolves: proliferate and counter-doubling effects let you keep climbing on a creature that has already hit the battlefield, which is the axis a static power-and-toughness mod could never offer.