Ryze, Rune Mage

Flash
When Ryze, Rune Mage enters the battlefield,
look at the top four cards of your library and
reveal one instant or sorcery spell from among
them and put it into your hand. Put the rest in
the bottom of your library in any order.
Whenever you cast your fourth instant or sorcery
spell this turn, exile Ryze, Rune Mage. Return
it to the battlefield under its owner's control at
the beginning of the next end step.