Cactuar

A 3/3 with trample for a single green mana is a rate the color has never handed out without a leash, so the return clause is the whole price. The tension is old: green wants enormous bodies cheap, and a cheap fatty always arrives with a string attached. Here the string is temporal rather than sacrificial, and the timing rewards a careful read, because it inverts the reflex. The return fires only if the creature did not enter this turn. Cast it on your turn and it survives untouched through your own end step, stays on the board across the opponent's turn, and then packs itself back to hand at your next end step (having, by then, entered a turn ago). That is the important cost buried in the timing: the body does not vanish, but it sits fully exposed to sorcery-speed removal on the opponent's turn between casts, and the bounce-recast cycle takes two of your turns to complete rather than resetting cleanly each end step. So it is not a here-and-gone flicker; it is a green beater that gets one full turn cycle to block and attack before it retreats. The design lives in that loop: a one-drop that reenters the battlefield each cycle to re-trigger other cards' enters-the-battlefield payoffs, and a mandatory return that doubles as insurance, since a bounced Cactuar cannot be caught by a sorcery-speed sweeper or graveyard hate on the turn it is safely in hand. The cost is paid not in life or cards but in the mana to keep recasting it, and in the window it can never fully close.