Shattered Grounds

At the beginning of each player's end step, that
player exiles face down a nontoken permanent
they own under Shattered Grounds.
Whenever there are seven cards exiled under Shattered Grounds, exile all permanents. Then,
turn face up the top card that was exiled under it.
Its owner may play it as though it has flash. If it's
a nonland card, they may cast it without paying
its mana cost. Repeat this process until all those
cards have been turned face up.