Olenna, Queen of Thorns

Creatures you control have hexproof. Creatures your opponents control lose hexproof.
Witty Quips—Whenever an opponent casts an
instant or sorcery spell, you may reveal a card from
your hand with the same mana cost. If you do,
counter that spell unless an opponent does the same.
"Ah yes, the famously tart-tongued Queen of Thorns."
"And the famous tart, Queen Cersei."
—Olenna Tyrell to Cersei Lannister