Ring of Thune is a uncommon Artifact — Equipment card from Game Night: Free-for-All (GN3), collector number 119. Current market price: $0.28, TCGplayer market prices via Scryfall.
Equipped creature has vigilance. (Attacking doesn't cause it to tap.) At the beginning of your upkeep, put a +1/+1 counter on equipped creature if it's white. Equip {1} ({1}: Attach to target creature you control. Equip only as a sorcery.)