The Circle of Loyalty is a mythic Legendary Artifact card from Dominaria United Commander (DMC), collector number 98. Current market price: $0.60, TCGplayer market prices via Scryfall.
Affinity for Knights (This spell costs {1} less to cast for each Knight you control.) Creatures you control get +1/+1. Whenever you cast a legendary spell, create a 2/2 white Knight creature token with vigilance. {3}{W}, {T}: Create a 2/2 white Knight creature token with vigilance.