Tengu format ruling
Rainbow Dragon
Card effect (current official text)(This card is always treated as an "Ultimate Crystal" card.)
Cannot be Normal Summoned/Set. Must be Special Summoned (from your hand) by having 7 "Crystal Beast" cards with different names on your field and/or GY. This card cannot activate the following effects the turn it is Special Summoned. (Quick Effect): You can send all face-up "Crystal Beast" monsters you control to the GY; this card gains 1000 ATK for each monster sent to the GY. You can banish all "Crystal Beast" monsters from your GY; shuffle all cards on the field into the Deck.
Rulings
- This card's effect to increase its ATK can be activated during the Damage Step. The ATK increase is applied as long as Rainbow Dragon remains face-up on the field.
- Sending the Crystal Beast monsters you control to the GY is a cost for Rainbow Dragon's first effect.
Rulings data courtesy of Format Library — formatlibrary.com. Spotted an inaccuracy? Flag it in the Tengu forum — sourced change requests get reviewed.