Swords of Revealing Light (EGS1-EN021) - Egyptian God Deck: Slifer the Sky Dragon Unlimited

After this card's activation, it remains on the field, but you must destroy it during the End Phase of your opponent's 3rd turn. When this card is activated: If your opponent controls a face-down monster, flip all monsters they control face-up. While this card is face-up on the field, your opponent's monsters cannot declare an attack.