Bone Shredder

Flying
Echo {2}{B} (At the beginning of your upkeep, if this came under your control since the beginning of your last upkeep, sacrifice it unless you pay its echo cost.)
When Bone Shredder enters, destroy target nonartifact, nonblack creature.

The List

March of the Machine Commander

Flying
Echo {2}{B} (At the beginning of your upkeep, if this came under your control since the beginning of your last upkeep, sacrifice it unless you pay its echo cost.)
When Bone Shredder enters the battlefield, destroy target nonartifact, nonblack creature.

Media Inserts

Modern Horizons 2

Duel Decks: Phyrexia vs. the Coalition

Paying for echo is always optional. When the echo triggered ability resolves, if you can't pay the echo cost or choose not to, you sacrifice that permanent.

Your permanent's echo ability will trigger at the beginning of your upkeep if it entered the battlefield since the beginning of your last upkeep, or if you gained control of it since the beginning of your last upkeep.