Patrolling Peacemaker is a rare Artifact Creature — Robot Soldier card from Edge of Eternities Commander (EOC), collector number 5. Current market price: $1.00, TCGplayer market prices via Scryfall.
This creature enters with two +1/+1 counters on it. Whenever an opponent commits a crime, proliferate. (They commit a crime if they target an opponent, anything an opponent controls, and/or cards in an opponent's graveyard. To proliferate, you choose any number of permanents and/or players, then give each another counter of each kind already there.)