Alacritous Pixie

Flying
{u}: Exile a noninstant, nonland card from your
hand. You may cast it for as long as it remains
exiled. Activate only as a sorcery.
Whenever you cast a noninstant spell during an
opponent's turn, put a flash counter on up to
one card exiled with Alacritous Pixie. (A spell
with flash may be cast any time its controller
could cast an instant.)