Mystic of Clouds and Sky

{t}: Target player exiles their library. If they
would draw a card they may draw it from the top
of their graveyard. Once per turn, that player
may sacrifice a permanent to play a card from
their exiled library without paying its mana cost.
If it is a creature it gains haste until end of turn.
At end of turn, bury it.
If Mystic of Clouds and Sky leaves play, return all exiled cards to their owner's library.