Mystical Tutor

Hold up one blue mana, watch the game develop, and answer whatever your opponent commits to: that deferral is the entire pitch for a one-mana search that finds any instant or sorcery. A sorcery-speed planner has to guess in advance which piece it wants; this finds the exact answer or combo component at the moment the question is actually being asked, which is why it has underpinned blue combo for decades, slotting into shells that want to assemble the kill on the turn they have already protected it. The price is paid in two places, both structural and both deliberate. First, it does not put the card in hand, only one draw away, so you owe a full upkeep of tempo before the thing you found can act. Second, the reveal clause forces full disclosure: a watchful opponent learns precisely which spell is coming and gets a turn to play around it. Selection bought in the open, not card advantage, is what keeps a one-mana tutor for any spell of its types from being broken. The shuffle is the third tax worth respecting, scrubbing whatever you had already arranged, so it wants to be cast when your next draw is not already spoken for. Vampiric Tutor performs the same job in black, trading the type restriction for a life cost and unrestricted targets; this is the blue, life-free version that pays its bill through type limits and the reveal.