Sins of the Past

Six mana, double black included, buys you exactly one free spell back from the bin, and the design pays for that flexibility with the heaviest possible terms: both the returned spell and this sorcery exile after the cast. That last clause is the real constraint. You are not building a loop here; you get one cast, the returned spell never touches your graveyard again, and the enabler is gone too. The effect is closer to a one-shot graveyard-flashback toolbox than a recursion engine, and at this rate it only justifies itself when the spell waiting in the yard is worth far more than its own mana cost: a board-clearing sorcery, a tutor, a game-ending instant you cast at the wrong moment the first time. The ceiling is genuine, because casting something "without paying its mana cost" ignores whatever made it expensive originally. The floor is brutal, because six mana to replay a single removal spell is a losing trade in almost any context. It belongs to the lineage of one-shot graveyard-recursion sorceries that try to recoup tempo by replaying your best spell, but where cheaper members of that family invite repetition, this one is deliberately terminal: the twin exile clauses make it a finisher's tool, not a value loop, and the cost ensures you reach for it only when the payoff dwarfs the investment.