Summoner's Egg

The trick is the timing inversion: imprint usually fires when the body enters and pays off immediately, but here the exiled card stays face down until the Egg dies, and only then does a creature card hatch onto the battlefield. That single delay turns a fragile 0/4 wall into a delivery vehicle that bypasses the entire payment for whatever you tucked away. Cast cost, color requirements, the cast step itself: none of it applies, because the creature is put onto the battlefield rather than cast. Hide a fatty you could never hardcast, then sacrifice or trade the shell to deploy it for free. The face-down exile is also pure information warfare; an opponent staring at a dead-looking Egg has no idea whether it is protecting a game-ending threat or a blank you dumped to dodge discard. The cost the design extracts is the body's own helplessness: a 0/4 that wants to die, on a clock you do not fully control, with the payoff hostage to the Egg surviving long enough to die on your terms rather than getting bounced or exiled out from under you. It rewards decks already running sacrifice outlets and cheap removal aimed at their own creatures, where the death trigger is something you cause rather than something you wait for. As a combo enabler, it belongs to the family of effects that cheat creatures into play by sidestepping the cast step, with imprint supplying the hidden-information wrinkle that straightforward reanimation never offered.