Idle, the Dreamer

Whenever you look at one or more cards from the top of an opponent's library, exile one of them face down (only you may look at it.)
Whenever a player shuffles a library, choose a card exiled with Idle, the Dreamer and turn it face up. Until end of turn, you may cast that card as though it had flash and spend mana as though it were mana of any color to do so.
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