Sleep

A sleeping creature starts with 3 sleep counters on it.
When a creature is put to sleep it becomes tapped
until all sleep counters are removed. Its controller
flips a coin at the beginning of each end step. If they
win the flip they remove 1 sleep counter from that creature.
Its controller removes 1 sleep counter from it during
their upkeep.
(Status Effect counters cannot be proliferated, and a creature cannot have more than one type of status
effect at a time.)