Grand Arbiter Leonos II

Eminence - At the beginning of each upkeep,
if Leonos is in the command zone or on the battlefield, name a card. Until end of turn, casting spells with that name is against the law.
{u}{w}, Sacrifice a Clue: Look at the top card
of each player's library. You may exile a card
you look at in this way. Otherwise, draw a
card.