The one they call The Shadow

Devour permanents you don't own 3 (As this
enters, you may sacrifice any number of permanents
you don't own. This creature enters the battlefield
with three times that many +1/+1 counters on it.)
Haste, menace
Whenever you sacrifice a permanent, you may have
The one they call The Shadow become an artifact
creature until end of turn. when you do, sacrifice it
at the next end step.