Dream Devourer

The last ability triggers when you exile a card from your hand using foretell, not when you cast a foretold card from exile.

If you foretell a modal double-faced card, the foretell cost will be based on the mana cost of the face you cast from exile. For example, if you foretell Kolvori, God of Kinship/The Ringhart Crest, you can cast Kolvori by paying {G}{G} or The Ringhart Crest by paying {G} on a future turn. If you foretell a modal double-faced card whose front face is a nonland face but whose back face is a land face, you can’t play that card as a land.

If you’re casting a foretold card from exile for its foretell cost, you can’t choose to cast it for any other alternative costs. You can, however, pay additional costs, such as kicker costs. If the card has any mandatory additional costs, those must be paid to cast the spell.