Bar'Dridel, Accursed Mage

Haste
When Bar'Dridel attacks, you may discard a card
from your hand. The player Bar'Dridel is
attacking exiles the top cards of their library
equal to half the total mana cost of the discarded
card rounded down. That player takes damage
equal to the total mana cost of those cards then
places those cards on the bottom of their library.