Avacyn, Angel of "Nope"

Flying, Indestructible
Flash-When this card enters the battlefield,
you may counter target spell.
Whenever an opponent casts a spell, you may
{1}Scry 1 (Instant) If the looked at card is a blue
spell, you may cast it in response to an
opponents spell, ignoring this card's ability on
the stack. If it is a white spell, you may pay for
its mana cost and exile it plus one
target permanent.
Angels can be blue too.