Invasion of Xerex // Vertex Paladin (MOM-242) - March of the Machine

(As a Siege enters, choose an opponent to protect it. You and others can attack it. When it's defeated, exile it, then cast it transformed.)
When Invasion of Xerex enters the battlefield, return up to one target creature to its owner's hand.

Flying
Vertex Paladin's power and toughness are each equal to the number of creatures you control.