Foretell lets you pay two mana during your turn to exile a card from your hand face down, then cast it on a later turn for its foretell cost. This spreads a spell's cost across multiple turns while concealing exactly what you've prepared.
Ranar the Ever-Watchful rewards cards being exiled and casting spells from exile, while Dream Devourer gives nonland cards in your hand foretell. The mechanic can make open mana particularly suspicious when several face-down cards are waiting in exile.
