Siphon Insight is a rare Instant card from Breaking News (OTP), collector number 54. Current market price: $0.23 (foil $0.32), TCGplayer market prices via Scryfall.
Look at the top two cards of target opponent's library. Exile one of them face down and put the other on the bottom of that library. You may play the exiled card for as long as it remains exiled, and you may spend mana as though it were mana of any color to cast that spell. Flashback {1}{U}{B}