Gem-Knight Ruby

Level 6 EARTH/Pyro Fusion Effect
2500 ATK / 1300 DEF

"Gem-Knight Garnet" + 1 "Gem-Knight" monster
Must first be Fusion Summoned with the above Fusion Material Monsters. Once per turn: You can Tribute 1 face-up "Gem-" monster; this card gains ATK equal to the Tributed monster's ATK on the field, until the End Phase. If this card attacks a Defense Position monster, inflict piercing Battle Damage to your opponent.

Rulings – Yugipedia

Printings:

Duel Terminal 5a: DT05-EN034 (Duel Terminal Ultra Parallel Rare) - 2011-05-29
Hidden Arsenal 5: Steelswarm Invasion: HA05-EN019 (Secret Rare) - 2011-12-01
Battles of Legend: Monster Mayhem: BLMM-EN136 (Ultra Rare) - 2025-08-28

Prices:

Cardmarket: 0.17 €
TCGplayer: $ 0.13