Blood Servitor is a common Artifact Creature — Construct card from Innistrad: Crimson Vow (VOW), collector number 252. Current market price: $0.25 (foil $0.11), TCGplayer market prices via Scryfall.
When this creature enters, create a Blood token. (It's an artifact with "{1}, {T}, Discard a card, Sacrifice this token: Draw a card.")