Plague Myr is a uncommon Artifact Creature — Phyrexian Myr card from Mirrodin Besieged (MBS), collector number 125. Current market price: $2.60 (foil $14.50), 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}.