Avalyn Summergale, Wanderer

Whenever a creature you control attacks, you may
pay {w} to give that creature first strike or {b} to
give that creature menace until end of turn.
(choose only one.) If you do, until end of turn as
long as that creature is on the battlefield,
Avalyn Summergale, Wanderer is unblockable.
"Uh guys, we need to get out of here."