Morgue Toad

A black creature that exists to die for blue and red. Sacrifice it and you get , the two colors that flank black on the color pie but that black cannot produce on its own: black makes black, so this body is the only socket through which a mono-black hand reaches its allied neighbors. That conversion explains why it wears a Frog suit instead of arriving as a mana artifact. The 2/2 is a delivery vehicle, but it is still a body, so until you cash it in it blocks, attacks, and sits on the battlefield as creature-shaped collateral for anything that profits from creatures dying. The tension is one of timing: the mana is locked inside something you have to spend the early game with, so you choose between a body now and two colors later, and you only get to choose once. As fixing it is slow and one-shot, strictly worse than a land that produces the same colors every turn; as a sacrifice payload it has a second life, because the death is the point rather than the cost. It is a curio of the era when designers were still working out how to make multicolor decks castable, a creature whose mana ability quietly hands you the pair of allied colors its own mana base could not otherwise tap for.