Card Appearances:Ancient Gear Reactor Dragon
- In episode 123, Yuri used this card in his Duel against Alexis Rhodes. He added this card to his hand with the effect of "Ancient Gear Wyvern" and summoned it by tributing "Ancient Gear Wyvern" and "Ancient Gear Gadget". This card then attacked one of Alexis's "Cyber Angel Natasha". Alexis attempted to use the effect of "Cyber Angel Natasha" to negate the attack, but Yuri told her that monster effects could not be activated while "Reactor Dragon" was attacking. This card destroyed "Natasha" as a result. Since this card was Tribute Summoned by tributing an "Ancient Gear" monster, it inflicted piercing damage to Alexis. Also, since this card was Tribute Summoned by tributing a "Gadget" monster, it could attack twice in the same Battle Phase, so it attacked and destroyed Alexis's second "Cyber Angel Natasha". This card then inflicted piercing damage to Alexis a second time. On Alexis's turn, she revived one of her "Cyber Angel Natasha" in Defense Position and used its effect to take control of this card. She then used "Natasha's" effect to gain Life Points equal to half the ATK of this card. Before she declared an attack, Yuri activated "Unfinished Ancient Gear", Special Summoning "Ancient Gear Golem" in Defense Position, ignoring the Summoning conditions, with its ATK and DEF halved and immunity to being destroyed by battle. This card then attacked "Ancient Gear Golem", inflicting piercing damage to Yuri. Due to its effect, it attacked "Ancient Gear Golem" a second time, inflicting piercing damage to Yuri again. On the last turn of the Duel, Yuri activated "Super Polymerization" to fuse this card on Alexis's side of the field with "Ancient Gear Golem" and "Ancient Gear Wyvern" on his side of the field and Fusion Summon "Ultimate Ancient Gear Golem".