Wildfire Devils

If the chosen player has no instant or sorcery cards in their graveyard, Wildfire Devils’s ability does nothing. You don’t pick a different player.

You choose a player at random and they exile a card all while the triggered ability is resolving. No player may take any actions between the two or between exiling the card and you copying and casting it.

If you cast a card “without paying its mana cost,” you can’t choose to cast it for any alternative costs. You can, however, pay additional costs. If the card has any mandatory additional costs, such as that of Momentous Fall, you must pay those to cast the card.