REDU format ruling
Seal of Wickedness

Nearest-era rulings (Tengu, Sept 2011) — no REDU-specific archive exists.
Card effect (current official text)Once per turn, during your opponent's Standby Phase, select 1 face-up card on the field. The selected card's effect(s) is negated during that turn. During each of your Standby Phases, pay 500 Life Points or destroy this card.
Rulings
- This effect targets 1 face-up card on the field. It targets that card continuously throughout the turn.
- Paying 500 Life Points is a cost, not an effect. It cannot be negated by "Royal Decree."
- If you target a "Gladiator Beast" monster with this effect, and your opponent returns it to the Deck to activate its effect, the effect will still be negated and the "Gladiator Beast" monster will remain in the Deck.
- If "Seal of Wickedness" targets itself, it will be negated for 1 turn. You can flip "Seal of Wickedness" and activate its effect in the same Chain.
- If "Seal of Wickedness" is destroyed, removed from the field, or negated while it is negating a card, its effects will no longer be applied and the selected card will no longer be negated.
- The effect to negate a card starts a Chain in the Standby Phase. It is a mandatory effect.
Rulings data courtesy of Format Library — formatlibrary.com. Spotted an inaccuracy? Flag it in the REDU forum — sourced change requests get reviewed.