Kadrav, Tracker of Essence

{1}{u}, {t}: Shuffle your library, then reveal the
top card of it. Put it into your hand if it's a
creature card, otherwise target opponent exiles
the top X cards of their library, where X is the revealed card's mana value. Activate this ability
no more than three times each turn.
Whenever you mesmerise, untap Kadrav,
Tracker of Essence.