Giant-Man, Gargantuan Genius

Green ramp has always paid you for lands, mana dorks, or the mere passage of turns; this pays you for size. Every creature you control with power 4 or greater becomes a green mana source once per turn, which inverts the usual big-creature economy: instead of ramp fueling fatties, the fatties are the ramp. The power-4 threshold does the balancing work, and it does it cleanly. It excludes the small utility creatures and mana elves you would otherwise lean on, so the engine pays out only after you have committed real bodies to the board. The card therefore wants a deck full of things that are individually threatening anyway, rewarding beef over tokens. Timing matters too: the mana appears during your precombat main phase, so it is green you spend recasting threats or feeding an X-cost payoff before combat, not mana you hold up for interaction. Its own 6/6 counts toward the tally, and reach keeps it useful on defense while the board fills out. Functionally this is closer to a Cryptolith Rite pointed at the top end than to a conventional ramp spell: a persistent, per-turn conversion of committed power into explosive mana, gated behind the requirement that you already field an army of large creatures. Where most ramp front-loads investment to reach the payoff, this one asks you to arrive at the payoff first, then rewards you for staying there.