Zio, the Riptide

When Zio, the Riptide enters the battlefield,
exile the top 4 cards of your library face down.
When Zio attacks, reveal up to two cards exiled
by Zio. Put creature cards revealed this way onto
the battlefield tapped and attacking. Return all
revealed cards to the bottom of your library at
the end of combat and exile two cards face down
from the top of your library.