Bloodhall Ooze

Twin upkeep triggers that read independently: a black permanent earns one counter, a green permanent earns another, and controlling both means two +1/+1 counters every turn. That is the whole conceit, a body that scales with how committed you are to a black-green core rather than to any single payoff. The design pays for an aggressive growth curve with a steep color tax: this is a 1/1 with no evasion and no protection, so the counters are only as fast as your second and third colors come online. In a mono-red shell it never moves at all, which is the constraint doing its work; the card rewards going wider, not generic efficiency. It sits among the small creatures that gate their payoff behind permanent types you control, and it does so without asking those permanents to do anything but exist. The wrinkle the design relies on is that the triggers check a permanent's actual color, not its name or type: a Swamp is colorless and will not feed the black trigger, so satisfying both conditions means having genuinely black and green permanents (creatures, enchantments, artifacts whose mana cost makes them those colors) on the battlefield at the start of upkeep. That keeps the deckbuilding cost honest: the ooze grows only as fast as you can spend on the two colors it cares about, and not a counter sooner.