Infernal Tutor

Empty your hand and this becomes an unconditional black tutor for two mana, fetching any card with no restriction whatsoever; keep cards in hand and it degrades into a redundant doubler that can only find a second copy of something you already hold. That gap between the two modes is the entire design, and it is what shaped the card into a combo enabler rather than a generic value tutor. Hellbent demands the cast happen as the last card in hand, or close to it, which dovetails with precisely the decks that want an unrestricted search in the first place: rituals, a payoff spell, and a plan to dump everything before going off. Spending your hand is the cost, and storm-style shells happily pay it, chaining mana and cantrips down to nothing before reaching for the piece that wins. At its weak mode, revealing a card to grab its twin, it patches a consistency problem. At its strong mode, it rivals the cheapest no-strings tutors black has ever printed, Demonic Tutor included. Most tutors fold their flexibility into the mana cost. This one folds it into a board state instead, withholding the full effect until you arrive at an empty hand, and the shells engineered to do that on purpose have always treated the restriction as a feature.