The Circle of Loyalty is a mythic Legendary Artifact card from Throne of Eldraine (ELD), collector number 336. Current market price: $4.10 (foil $10.00), 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.