Murdok, The Wordsmith

When Murdok, The Wordsmith enters the
battlefield, exile the top card of each player's library.
Until end of turn you may cast nonland cards
from among those exiled cards, you may spend
mana as though it were mana of any color to cast
those spells.
At the beginning of the next end step, if any of
those cards remain exiled, put them into play under its owners control.