Boarback Charger

Trample
Whenever Boarback Charger attacks or blocks,
you may discard a card. If you do, mill a card
until the total mana value of cards milled this
way is greater than the discarded card's mana
value or you choose to stop milling. If the total
mana value of the milled cards is less than or
equal to the discarded card's mana value,
Boarback Charger gets +2/+0 until end of turn
for each milled card.