Timbermare

The entry trigger taps every other creature on the board, the caster's included, but the asymmetry it sells is one of timing: this 5/5 already has haste, so it arrives swinging into a field where nothing can block. Mass-tap effects were long the province of blue's Sleep-style tempo plays; bolting one onto a green beater that immediately exploits the standstill it creates is the design conceit, and the attack matters more than the creature you keep. Echo is what prices that trick honestly. Four mana puts the Horse down, then comes due at your next upkeep or it sacrifices itself, nearly double the deployment cost for a body with no second ability worth keeping around. The intended line is to never pay: cash the global tap and the five-point swing the turn it lands, take whatever value that buys, and let it die rather than re-purchase a spent 5/5. That structure makes it a one-shot tempo burst wearing a creature's clothes, where the haste, the board-wide tap, and the unpaid echo collapse into a single decisive turn and then it leaves.