As Shapeshifter enters the battlefield, choose a number between 0 and 7.
At the beginning of your upkeep, you may choose a number between 0 and 7.
Shapeshifter's power is equal to the last chosen number and its toughness is equal to 7 minus that number.
Born like a Phoenix from the Flame, But neither Bulk nor Shape the same. —Jonathan Swift, "Vanbrug's House"