Mage's Guile is a common Instant card from Onslaught (ONS), collector number 91. Current market price: $0.22 (foil $4.18), TCGplayer market prices via Scryfall.
Target creature gains shroud until end of turn. (It can't be the target of spells or abilities.) Cycling {U} ({U}, Discard this card: Draw a card.)