Savvath, Ancient Patron

Changeling (This card is every creature type.)

When Savvath, Ancient Patron enters, each player exiles the top X cards of their library. Savvath becomes a copy of a creature card exiled this way, except it's name is Savvath, Ancient Patron, it's
a 5/4 legendary creature in addition to it's other types, and it has changeling and "{3}{u}: Return Savvath, Ancient Patron to it's owners hand, then draw a card."