Plague Myr is a uncommon Artifact Creature — Phyrexian Myr card from Phyrexia: All Will Be One Commander (ONC), collector number 139. Current market price: $3.14, TCGplayer market prices via Scryfall.
Infect (This creature deals damage to creatures in the form of -1/-1 counters and to players in the form of poison counters.) {T}: Add {C}.