冲锋机械

Extruder can be the target of its own activated ability, and you can sacrifice Extruder to pay for that activation. This won't accomplish much, but it does allow you to sacrifice Extruder if you want to.

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.