Oathkeeper, Takeno's Daisho is a rare Legendary Artifact — Equipment card from Champions of Kamigawa (CHK), collector number 265. Current market price: $16.29 (foil $48.64), TCGplayer market prices via Scryfall.
Equipped creature gets +3/+1. Whenever equipped creature dies, return that card to the battlefield under your control if it's a Samurai card. When Oathkeeper is put into a graveyard from the battlefield, exile equipped creature. Equip {2}