Demonic Tutor

The shortest possible distance between a deck and its best card, priced at two mana with no restriction, no life cost, no graveyard exile, no reveal. Every unconditional tutor that came after it had to find some way to be worse: Vampiric Tutor moves the card to the top of the library instead of the hand and charges life; Imperial Seal stacks a sorcery-speed restriction on top of that; Diabolic Tutor doubles the mana cost; Grim Tutor asks for three life and a third mana. The design lesson encoded here is that "search your library for a card" with no adjective in front of "card" is the most powerful sentence black can write, and the rate at which it first appeared was a calibration error the game has spent three decades declining to repeat. What makes the card load-bearing is less the effect than the pricing: at two mana, the tutor resolves before most decks have done anything, which means the deck casting it gets to assemble its plan a turn ahead of the deck answering it. That asymmetry has earned the card a ban or restriction in every competitive format that ever had to weigh it, and its presence in a format reads as a statement about what kind of format the designers want it to be.