Aria, The Lady Clairvoyant

This can't be blocked as long as you control
no other creatures.
Whenever Aria, The Lady Clairvoyant attacks,
exile the top four cards of your library.
Until end of turn, you may cast noncreature
cards exiled with Aria this turn without paying
their mana costs.
"In the gloomiest hour, one will rise, and her
power will obliterate the shadow of darkness."