Mayan Calendar

As Mayan Calendar enters the battlefield,
secretly choose a Number between 4 and 10.
Each Time a player other than you Casts a Spell,
Mayan Calendar Gains 1 Apocalypse Counter.
When Mayan Calendar has an amount of
Apocalypse Counters that is equal to the
number you chose, Sacrifice Mayan Calendar,
Exile All Permanents Each player Controls.