Delve the Eternities

Flashback {5}{w}{b}
Forgotten — {1}{w}, Turn this card face-down:
Until end of turn, you may play face-up cards in
exile and you may spend mana as though it were
mana of any color to cast those spells. If a spell
cast this way would be put into a graveyard this
turn, exile it face-down instead. Activate this
ability only if this card is face-up in exile.
Exile target nonland permanent.