Diabolic Tutor

Search your library for any card, no conditions attached: no creature type to surrender, no colored-pip puzzle, no life billed, no card-type fence. The function is identical to Demonic Tutor; the gap is the tax. Where that card asks two mana and a single black pip (and answers for it with a spot on the Restricted list), this one charges four, and the difference between them is the most legible illustration in the game of what unconditional flexibility is worth. That price is why this version has been a casual fixture for two decades, reprinted into core and starter products again and again, while its cheaper twin lives in formats that police it. Four mana is the rate that keeps an open-ended search honest when the deck is not a combo engine racing to assemble pieces a turn early.

That makes it the baseline for the whole black-tutor design space. Every searcher Wizards prints sits somewhere between these two poles: Diabolic Intent wants a creature to feed it, Beseech the Queen prices itself in colored pips, Vampiric Tutor puts the card on top instead of in hand and charges life for the discount. Each one is negotiating down from four-mana-to-hand or up from two. This is the card you reach for when the deck cannot afford a steeper restriction and can spare the turn: the searcher built for everyone not optimizing a competitive kill.