Goat format ruling
Curse of Fiend
Card effect (current official text)Change the battle positions of all Attack Position monsters on the field to Defense Position and vice-versa. These positions cannot be changed during the turn this card is activated except by the effect of a Spell, Trap or Effect Monster Card. You can only activate this card during your Standby Phase.
Rulings
- 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.
- 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.
Rulings data courtesy of Format Library — formatlibrary.com. Spotted an inaccuracy? Flag it in the Goat forum — sourced change requests get reviewed.