Face-down Defense position monsters will be changed to face-up Attack position by the effect of “Curse of Fiend.” Any applicable Flip Effects will activate at that time.
Monsters affected by “Curse of Fiend” may have their battle positions changed by effects.
Netrep Q&As:
Q: Does “Curse of Fiend’s” effect work on Set monsters and would it be considered a Flip Summon?
A: A Set monster would be changed to face-up attack position. It would not be considered Flip-Summoned, because its position was changed by a card effect, but its Flip-Effect would activate if it had one. Curtis Schultz, 01/25/2004