Corpse Cobble

Instant-speed board conversion is the whole trick here. Sacrifice effects that mass a token off your creatures' power usually cost a card and a sorcery step, but this one fires in response to a board wipe, an unblocked attacker's death, or the combat-math window where your opponent has already committed blockers. You feed a doomed board into a single menace threat whose size scales with everything you put in, and because it is an instant, the timing lets you dodge the removal that would otherwise pick the pieces apart. The menace keyword is the payoff clause: a big token that trades one-for-one into a chump block is not a payoff, so the design insists the resulting body actually gets through.

Flashback turns a one-shot combat trick into a recurring finisher. Because the additional cost is paid by sacrificing creatures currently on the battlefield, the second casting rewards a deck built to keep restocking bodies rather than one that empties its board once: you need a fresh crop of creatures in play to fold into the second token. That two-act structure, cast now off a committed board and again later once you have rebuilt one, is the reason this reads less like removal insurance and more like a sacrifice deck's closer: the first token stabilizes, the second finishes an opponent who thought they had traded down the threat. Exiling the card after its flashback caps the loop, so a deck cannot recur it indefinitely.