Tengu format ruling
Rainbow Dark 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 banishing 7 DARK monsters with different names from your GY. You can banish all other DARK monsters from your field and GY; this card gains 500 ATK for each card banished this way.
Rulings
- Rainbow Dark Dragon's effect to increase its ATK is an Ignition Effect.
- Removing from play all other DARK monsters you control and in your GY is a cost.
Rulings data courtesy of Format Library — formatlibrary.com. Spotted an inaccuracy? Flag it in the Tengu forum — sourced change requests get reviewed.