Armageddon Clock

A symmetric doomsday device, and a clock the whole table has to manage. The shape is pure Antiquities-era artifact design: a global threat that ratchets up on its own, with a release valve any player can pay into. The four-mana activation is the interesting half. Because anyone can pay it, but only during an upkeep, the card turns into a recurring negotiation: who is closest to dying, who can afford to spend four mana this turn, and who benefits from letting the counters climb one more cycle. The upkeep restriction is what keeps the puzzle honest. Removal can only happen during an upkeep step, which sits before the draw step where the damage actually lands, so the table has to commit to paying the toll before the trigger is even on the stack. That ordering also means the active player draws for the turn ahead of taking the damage, and that whoever is already behind feels every counter most. The rate is slow by modern standards (six mana to deploy, then a turn before it does anything), but the design template (a symmetric escalating threat with a shared off-switch) has been revisited many times since, and almost never with this much willingness to let the table sort it out.