Solitary Confinement

The protective shell here is total: shroud you cannot strip off, damage prevention nothing pierces, an enchantment that turns its controller into a fortress no spell can touch and no burn can reach. Total protection invites a total price, and the cost is metered out of the hand. The card runs on cards in hand and nothing else. You skip your draw step and then feed it a discard every upkeep, so the lock costs you a card a turn while choking off the natural means of replacing it: a net two-card hole opening every upkeep that an ordinary deck simply cannot fill. That math only works for a deck engineered to refill faster than it bleeds, with a draw engine that ignores the skipped draw step entirely (Necropotence converting life into hand, or an Enchantress shell drawing off its own enchantment chains) so the upkeep discard becomes fuel rather than a tax. Pairing it with Genesis is the canonical version: the discarded creature returns each upkeep, so the cost literally hands itself back. What makes this a sharp design rather than a clumsy life-ward is that it concedes nothing in either direction. With the prison fully assembled you are immune to attacks, burn, targeted removal, and most win conditions while you assemble the kill at leisure. The shroud cuts both ways (your own targeted effects cannot reach you either), but a deck committed this far to the lock rarely has cause to aim anything inward.