World Cleansing

Shroud
As an additional cost to this spell pay 5 life.
World Cleansing enters the battlefield with 1 time counters.
At the beginning of your upkeep remove a charge counter from World Cleansing.
Any player may sacrifice a creature and pay 5 life to add a time counter to World Cleansing.
If World Cleansing has no counters on it, Exile all permanents.