Ahri, The Ninetailed Fox

First Strike.

During your combat phase, when Ahri strikes a creature your opponent controls, swap her blocker with another target creature your opponent controls. Ahri and target creature strike each other. If a creature you control was originally blocking target creature, return the creature you control to your hand.

Level up (If you've returned five or more creatures to your hand, grant Ahri +1/+1, flying, and "When Ahri returns a creature you control to your hand, reduce its cost by 1.")