Iuvenium, Inevitable Rapture

You may only play one copy of Iuvenium,
Inevitable Rapture in your deck.
If Iuvenium is in your opening hand and you
take a mulligan, you get a rapture counter.
Exile Iuvenium from your hand, remove a
rapture counter from yourself: Exile all
permanents, then create a 4/4 Angel token with
flying. This ability can't be countered. Activate
this ability only if you control five or more plains.
"Enlightenment approaches." -Avacyn