Flying
When this creature enters, exchange control of this creature and up to one target creature an opponent controls. If you don't or can't make an exchange, sacrifice this creature. This ability still resolves if its target becomes illegal.
Trample
Cumulative upkeep—Put a +1/+1 counter on a creature an opponent controls. (At the beginning of your upkeep, put an age counter on this permanent, then sacrifice it unless you pay its upkeep cost for each age counter on it.)
