Bilbo's Ring is a mythic Legendary Artifact — Equipment card from The Hobbit Commander (HOC), collector number 41. Current market price: $8.24 (foil $9.44), TCGplayer market prices via Scryfall.
During your turn, equipped creature has hexproof and can't be blocked. Whenever equipped creature attacks alone, you draw a card and you lose 1 life. Equip Halfling {1} ({1}: Attach to target Halfling you control. Equip only as a sorcery.) Equip {4} ({4}: Attach to target creature you control. Equip only as a sorcery.)