Eldritch Arcanist

Ward {2}
{1}{u}, {t}: Mill 6 cards.
{t}, Exile any number of instant and sorcery
cards from your graveyard with total mana
value X: You may cast target instant or sorcery
in your graveyard with mana value X without
paying its mana cost this turn. When you do,
exile it as it resolves.