Sun Tzu, Master of Strategy

Horsemanship, Vigilance
Know Thy Self — You may look at the top card
of your library at any time.
Know Thy Enemy — Your opponents play
with the top card of their library revealed
{u}{b}{t}: Each player mills a card. Sun Tzu gets
+X/+0 until end of turn, where X is the total
mana value of each card milled in this way.