Sylen, Scribe of the Forgotten

Whenever you draw a card, untap Sylen, Scribe
of the Forgotten.
{b}, {t}: Exile target card in a graveyard.
{t}: Until the beginning of the next end step, you
may cast target card exiled with Sylen, Scribe of
the Forgotten. You may spend {u} as though it
were any color of mana to cast it.