Chameleon Colossus

The pump ability scales the way a runaway should: each activation reads current power, so the bonus doubles every time you pay for it. Four mana takes the body from 4/4 to 8/8, another four makes it 16/16, and the climb steepens from there as fast as your mana lets it. That exponential growth is the design idea, and protection from black is the counterweight that keeps a green fatty from folding to the color built to kill it. Black leans hardest on targeted destruction, and the Colossus shrugs off all of it: no black removal spell can target it, no black creature can block or damage it, no black aura can stick. The hole in that armor is the edict, the sacrifice-a-creature effect that names the player rather than the creature; protection does nothing there, so Diabolic Edict or Liliana of the Veil can still pry it loose. Changeling is the quieter half. Counting as all creature types lets this Shapeshifter drop into any tribal shell as a top-end body, the role it was built for in an era that pushed creature-type synergies hard. The two abilities want different things: one asks you to find a tribe to belong to, the other asks you to dump mana into a single threat and end the game. The mana sink is the more durable identity, because a 4/4 that grows arbitrarily large for a repeatable, fixed cost is a finisher in any green deck willing to flood the late game.