Subterranean Shambler

The damage trigger fires twice for the price of one creature: once when it enters, once when it leaves. That symmetry is what the design is built around, and echo is the lever that pulls it. Pay the echo cost and you keep a serviceable blocker around; decline it, and the creature sacrifices itself on your next upkeep, throwing the second point of damage at every nonflyer on the way out. So the card plays as a two-shot board sweep against decks of small ground creatures, with the decision deferred to the upkeep where you can read the board first. Echo as a mechanic usually punishes you with a tempo tax for a body you wanted anyway; here the design inverts that, turning the sacrifice clause into a feature, because leaving the battlefield is itself a payoff. The single point of damage looks slight, but two staggered pings clear the X/1s and soften the X/2s that early-era aggressive ground decks leaned on, and the flying exemption keeps your own evasive threats clean. A modest 2/3 wrapped around a sweeper you trigger twice and pay for once.