Basal Thrull

A ritual stapled to a body, which is a stranger design than it sounds. The card invests two black mana into a 1/2, then lets that creature cash itself back in for two black mana whenever you need it: net-zero on mana, but it parks the value on the battlefield until you want to release it. That makes it less a Dark Ritual variant than a fixed-position fuse. Dark Ritual gives you the burst now or never; this gives you the burst later, on a turn of your choosing, with a blocker holding the fort in the meantime. The summoning-sick window and the sacrifice clause are what hold the rate in check: you cannot deploy it and detonate it the same turn, and once it pays out it is gone, so the mana it stores is borrowed against the creature it ceases to be. This is black acceleration for a deck with one expensive payoff to lunge toward rather than a curve to smooth, since the body is mediocre and the activation is a one-time spike rather than a recurring engine. The Thrull was the recurring servant-creature of its set's flavor, bred and discarded by the noble houses, and the card's mechanical identity (a thing whose entire purpose is to be spent) reads as deliberate.