Rainbow Overdragon

Level 12 LIGHT/Dragon Fusion Monster
4000 ATK / 0 DEF

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.

Rulings – Yugipedia

Printings:

Legendary Duelists: Ancient Millennium: LED2-EN037 (Super Rare) - 2018-02-22
Legendary Duelists: Season 1: LDS1-EN101 (Ultra Rare) - 2020-07-02
Speed Duel GX: Duel Academy Box: SGX1-ENF21 (Common) - 2022-03-17
Structure Deck: Legend of the Crystal Beasts: SDCB-EN043 (Super Rare) - 2022-09-29

Prices:

Cardmarket: 0.11 €
TCGplayer: $ 0.10