Doomsday

Search your library and graveyard for five cards
and exile the rest. Put the chosen cards on top of
your library in any order. You lose half your life, rounded up.
"You've helped me grow strong, you've provided the
means by which I can obtain Princess Twilight's
magic, and now you are no longer of any use to me."
-Tirek To Discord, Twilight's Kingdom - Part 2