Strix, the Light Breeze

Flying, Lifelink, Planeswalk (If this creature
would leave the battlefield, instead exile it
with a planar counter on it for each creature
you control.)
Whenever a creature is exiled, if this creature
is in exile, remove a counter from it. then if
there are no planar counters on it, you may return
it to the battlefield under its owner's control
Whenever a creature you control with flying
enters the battlefield, exile target creature.