REDU format ruling
The Dragon's Bead

Nearest-era rulings (Tengu, Sept 2011) — no REDU-specific archive exists.
Card effect (current official text)Discard 1 card from your hand. Negate the effect of a Trap Card that targets 1 face-up Dragon-Type monster and destroy the Trap Card.
Rulings
- When you first activate this card (flip it face-up) you do not have to activate its effect.
- If The Dragon’s Bead is already face-up on the field, you may activate it multiple times in the same chain, but you must discard 1 card from you hand as a cost for each activation.
- You cannot activate the effect of The Dragon’s Bead during the Damage Step.
- You cannot activate the effect of The Dragon’s Bead to negate a Trap Card that has already resolved, such as a Nightmare Wheel the opponent activated on a previous turn.
- You can only activate the effect of this card to negate a Trap Card that targets a face-up Dragon-Type monster, so it cannot negate Mirror Force, Waboku, Torrential Tribute, Bottomless Trap Hole, etc.
Rulings data courtesy of Format Library — formatlibrary.com. Spotted an inaccuracy? Flag it in the REDU forum — sourced change requests get reviewed.