Hemyrea, the Everdark

Flying, Lifelink, Siphon (Whenever this creature
deals combat damage to a player, that player mills
that many cards.)
Whenever an opponent would mill one or more
cards, exile those cards face down instead, and
put a void counter on them. For as long as those
cards remain exiled, you may look at them and
cast them, using mana as though it were mana of
any colour to do so.