Merciless Resolve

The additional cost is the whole conversation here, and it's a more forgiving one than black card-draw usually demands. Sign in Blood and its descendants pay in life; this one lets you turn something already on the battlefield into two fresh cards, and crucially it accepts a land as readily as a creature. The land clause is what pulls it clear of the pure sacrifice payoffs that only fire when a body dies: late in a game, when you're flooded and your draws are dead, a tapped-out land you no longer need converts straight into card advantage at instant speed. The flexibility cuts both ways, of course, since you're still trading a permanent for the cards rather than getting them free, but the instant-speed window lets you sacrifice in response to removal, dig on an opponent's upkeep or draw step, or feed a chump blocker into the spell rather than into a doomed combat. It reads like a small card, and it is, but the design is quietly aware of the worst moments in a game (no creatures to spare, or too much mana and nothing to spend it on) and hands you an exit either way. A draw spell that asks you to convert what you have too much of into what you don't is a tidy answer to the resource imbalances that midrange black decks run into more often than they'd like.