Edison format ruling
Fairy Box

Card effect (current official text)When your opponent's monster declares an attack: Toss a coin and call it. If you call it right, the attacking monster's ATK becomes 0 until the end of the Battle Phase. During each of your Standby Phases, pay 500 Life Points or destroy this card.
Rulings
- If you have two copies of Fairy Box active on the field you may flip a coin twice, but only need to call 1 correctly to reduce the attacking monster’s ATK to 0.
- The current ATK is reduced to 0, including all Equip Spell Cards. Trap Cards and Quick-Play Spell Cards cannot further increase the monster’s ATK this battle. A monster effect such as Injection Fairy Lily can increase its own ATK after Fairy Box is successful.
- Paying 500 Life Points is optional, if you choose not to pay Fairy Box is destroyed.
- The effect of Fairy Box does not target, so Lord of D. will not prevent Fairy Box from reducing the ATK of an attacking Dragon-Type monster to 0.
Rulings data courtesy of Format Library — formatlibrary.com. Spotted an inaccuracy? Flag it in the Edison forum — sourced change requests get reviewed.