Watcher

Cannot attack
On your combat phase, you may choose target creature on the battlefield. That creature loses all abilities until Watcher leaves the battlefield, and
gets a -0/-1 counter on your end step if it's not an artifact. You may only choose one creature at a
time.
—
They're passive creatures, but that doesn't make them
any less dangerous. Under it's gaze, even the most
level-headed of people lose their minds.