Infernal Plunge

One red mana goes in, three red mana comes out, so a single card nets you two mana toward an explosive turn. The catch sits in the additional cost: you have to feed a creature into it, which means the spell is dead on an empty board and live only in a deck that treats bodies as disposable fuel. That distinguishes it from rituals like Dark Ritual or Pyretic Ritual, which ask for nothing but mana up front. Here the sacrifice is the whole design tension: in a token-soaked or aristocrats build (undying creatures, anything with a useful death trigger), the cost is a second payoff rather than a real expense, and the burst of mana arrives off a permanent that was already on its way to the graveyard. Outside that context it is a trap, because trading a creature plus a card for a fistful of red mana you must spend immediately is a brutal tempo swing if the payoff turn does not close the game. It reads like a ritual but functions as a combo enabler, sharp only in the narrow window where the sacrificed creature was earmarked to die anyway.