flying
as jumbo imp enters the battlefield, roll a six-sided die. jumbo imp enters the battlefield 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 jumbo imp 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 jumbo imp equal to the result.