Creatures gain cooldown X this turn, where X is equal to the number of creatures on the battlefield.
Destroy all creatures, then cooldown 9 Overprime. (Exile Overprime with nine time counters on it. At the beginning of your upkeep, remove a time counter. When the last counter is removed, return Overprime to your hand.)
For Challenge # 146. See also Cracked Wheel.