Kirby, the Copying Puffball

When Kirby enters the battlefield, exile target creature with mana value X until Kirby leaves
the battlefield, then Kirby becomes a copy of
that creature
Hammer- {2}{r}: Kirby deals 2 damage to target creature. If this ability is activated more
than once in a turn, Kirby deals two extra
damage to that creature per time this ability has
been activated