Root Elemental

Flipping this face up turns a generic 2/2 into a 6/5 and, in the same gesture, smuggles a creature out of your hand and onto the battlefield for free. That second clause is the real engine: the morph cost of buys not just the Elemental's body but a second creature with no further payment, the morph trigger functioning as a one-shot cheat-into-play that ignores the entered creature's own mana cost. The natural targets are the things you would never want to hardcast: an oversized fattie, a creature with a punishing summoning cost, anything where the mana saved exceeds the ten you sank into the morph and unmorph. The face-down disguise adds a layer of bluff to the deal, since an opponent cannot know whether the 2/2 is a beater, a combat trick, or a delivery system for something far worse. The arithmetic rarely flatters it (you are paying a lot of green to net a body and a payoff), but the design is doing something morph specializes in: stapling a hidden second event onto a creature that already looks like a finished threat. It is a green take on reanimator logic that never touches the graveyard, pulling the big thing straight from hand instead.