Emrakul's Hatcher

The five mana you pay buys a 3/3 body and, more to the point, three Eldrazi Spawn that each cash in for a colorless mana later. Read the math forward and this is a creature that refunds three of its five mana, just deferred: cast it and you have effectively banked toward a larger spell next turn, or three sacrifice bodies for an outlet, or a fixed pile of chump blockers. That deferral was the whole reason the Spawn-makers existed in the first place: the Eldrazi colossi sat at the top of their curve at costs no honest manabase could reach, and the acceleration that fed them came stapled to small red bodies rather than to lands or green dorks. Putting the ramp on a creature, and one that arrives as four separate bodies, is what gives this an edge over a Rampant Growth: it advances the board while it advances the mana, and the Spawn keep their value even in a game where the giant payoff never comes. The cost is that the mana is locked into a one-shot sacrifice and the tokens are 0/1s that do nothing on offense, so the engine only pays out if you have somewhere for the colorless to go. Among the red Spawn-generators, this hands you the most mana per body with the least conditional text: no upkeep clause, no attack trigger, just three tokens and a clean 3/3.