Gem-Knight Master Diamond

Level 9 EARTH/Rock Fusion Monster
2900 ATK / 2500 DEF

3 "Gem-Knight" monsters
Must first be Fusion Summoned. This card gains 100 ATK for each "Gem-" monster in your Graveyard. Once per turn: You can banish 1 Level 7 or lower "Gem-Knight" Fusion Monster from your Graveyard; until the End Phase, this card's name becomes that monster's, and replace this effect with that monster's original effects.

Rulings – Yugipedia

Printings:

Duel Terminal 7b: DT07-EN083 (Duel Terminal Ultra Parallel Rare) - 2013-02-01
Hidden Arsenal 7: Knight of Stars: HA07-EN059 (Secret Rare) - 2013-04-26
Star Pack ARC-V: SP15-EN030 (Common) - 2015-06-12
Star Pack ARC-V: SP15-EN030 (Shatterfoil Rare) - 2015-06-12
Quarter Century Stampede: RA04-EN178 (Platinum Secret Rare) - 2025-04-10
Quarter Century Stampede: RA04-EN178 (Quarter Century Secret Rare) - 2025-04-10
Battles of Legend: Monster Mayhem: BLMM-EN143 (Ultra Rare) - 2025-08-28

Prices:

Cardmarket: 0.25 €
TCGplayer: $ 0.09