Rainbow Overdragon (LED2-EN037) - Legendary Duelists: Ancient Millennium 1st Edition

7 "Crystal Beast" monsters
(This card is always treated as an "Ultimate Crystal" card.)
Must be either Fusion Summoned, or Special Summoned by Tributing 1 Level 10 "Ultimate Crystal" monster (in which case you do not use "Polymerization"). Once per turn: You can banish 1 "Crystal Beast" monster from your GY; this card gains ATK equal to the banished monster's, until the end of this turn. (Quick Effect): You can Tribute this Fusion Summoned card; shuffle all cards on the field into the Deck.