Akroan Horse

The myth made literal: a gift you hand your enemy that turns out to be a slow leak, only the leak drains outward from whoever is stuck holding it. The whole design pivots on the donation. You give an opponent a 0/4 defender that does nothing for them on its face, and from that point the upkeep trigger fires on their turn, generating a 1/1 white Soldier for each of their opponents. So the recipient commands the Horse but is the one it works against, spitting out bodies for everyone arrayed against them, you included. The inversion of incentives is the engine: the donor wants the gift to linger; the recipient wants it gone but cannot easily attack with a defender or extract value from a creature that only ever arms the room. What makes it useful to the giver is that the tokens all land in front of the table's other players, so the Horse rewards a build that can monetize a drip of creatures it did not spend cards to produce: sacrifice payoffs, go-wide finishers, anything that turns a recurring 1/1 into more than a chump blocker. The control-change on entry is the wrinkle the rest of the card hangs on. You keep ownership while the opponent merely commands the thing feeding their rivals, and the design commits fully to that premise: the trick only pays if you can capitalize on the small army your enemy is now forced to grow for the benefit of everyone but themselves.