Doomsday Excruciator

The symmetry is the whole design gamble. When it lands off a hard cast, each player loses everything but the bottom six cards of their library: a mass exile that empties the caster's deck as thoroughly as the opponent's. That is a strange thing to hang on a creature that also has to survive. What tilts the symmetry is the second clause, an upkeep draw that begins working the turn after: with only six cards left in your own library, a repeatable extra draw is not card advantage so much as a countdown, and every turn spent building toward decking is a turn the opponent has been reduced to the same six-card cliff. The six-black-pip cost is the price of admission, and it is a wall in any deck not committed to a single color; the reward is a 6/6 flier that turns the game into a race to convert a hollowed-out library into a win before the draw step catches up to you. The "if it was cast" rider is the quiet safety valve: reanimate or blink it and the exile never fires, so the effect is bolted specifically to casting it rather than cheating the body onto the battlefield. Less a value engine than a puzzle box, it asks you to weaponize the shortest clock in the game against yourself first.