Erina, Magical Girl

{w}{w} Tap 2 target cards
Each time this card attacks, roll a D20
adding +2 to the result for each Counter
on this card. If you get a result of 20,
target card is destroyed. If you don't,
tap this card and add a Counter to this
card. For every 10's place you reach, you
may destroy an additional creature as
well as the original target