Aliva, Dean of Nullification

{w}{u}{b},{t}, Exile a nonland card from your
graveyard: Counter target spell that shares a card
type with the exiled card unless its controller
pays {x}, where X is the mana value of the exiled
card. If that spell is countered this way, exile it,
then choose one:
• You may cast a spell with lesser mana value
that shares a card type with the exiled spell from
your hand without paying its mana cost.
• Draw a card. If you do, discard a card.