Knighted Myr is a common Artifact Creature — Myr Knight card from Commander Masters (CMM), collector number 36. Current market price: $0.30 (foil $0.21), TCGplayer market prices via Scryfall.
{2}{W}: Adapt 1. (If this creature has no +1/+1 counters on it, put a +1/+1 counter on it.) Whenever one or more +1/+1 counters are put on this creature, it gains double strike until end of turn.