Olivia, Ravenous Exile

Flying
Whenever an opponent discards one or more
cards, put a +1/+1 counter on up to one target
Vampire you control.
{1}{r}{p/w}{b}, {t}: Target opponent discards a card.
If that player has no cards in hand, untap all
Vampires you control and transform Olivia,
Ravenous Exile. Activate only as a sorcery.