Flying
As this creature enters, roll a six-sided die. This creature enters with a number of +1/+1 counters on it equal to the result.
At the beginning of your upkeep, roll a six-sided die and put a number of +1/+1 counters on this creature equal to the result.
At the beginning of your end step, roll a six-sided die and remove a number of +1/+1 counters from this creature equal to the result.