Floating Shield is a common Enchantment — Aura card from Torment (TOR), collector number 5. Current market price: $0.15 (foil $1.15), TCGplayer market prices via Scryfall.
Enchant creature As this Aura enters, choose a color. Enchanted creature has protection from the chosen color. This effect doesn't remove this Aura. Sacrifice this Aura: Target creature gains protection from the chosen color until end of turn.