"123 Fusion Destruction", known as "The Glorious Machine Dragon" in the Japanese version, is the one hundred and twenty-third episode of the Yu-Gi-Oh! ARC-V anime. It first aired in Japan on September 18th, 2016 and in Canada on December 30, 2017. It became available with official subtitles via Crunchyroll on November 22, 2017.
Yusho and Declan run into each other in Duel Academy. It is then that Yuri attacks them. In order for Yusho to be able to reach the Professor, Alexis stands against Yuri. Facing off against Yuri, who flashes a wicked smile at her and uses an "Honor Student Deck" that is given to Duel Academy's chosen ones, Alexis tries to convey Yusho’s "bring smiles through Dueling" ideal. With both having been students of Duel Academy, what will be the outcome of this battle?
Turn 2: Yuri Yuri activates the Continuous Spell Card, "Ancient Gear Fortress", preventing "Ancient Gear" monsters he controls from being targeted or destroyed by his opponent's card effects during the turn they are Normal or Special Summoned. It will also prevent the opponent from activating any cards or effects in response to the activation of any "Ancient Gear" card. As he controls no monsters, Yuri activates "Ancient Gear Catapult", letting him target and destroy a face-up card he controls and Special Summon an "Ancient Gear" monster from his Deck, ignoring the Summoning conditions. He destroys "Fortress" and Special Summons "Ancient Gear Gadget" (500/2000). As "Fortress" was destroyed, its effect activates, letting Yuri Special Summon an "Ancient Gear" monster from his hand or Graveyard, but he may not Special Summon any monsters for the rest of this turn except "Ancient Gear" monsters. He Special Summons "Ancient Gear Wyvern" from his hand in Attack Position (1700/1200). As it was Normal or Special Summoned, its effect activates, letting Yuri add an "Ancient Gear" monster from his Deck to his hand. He adds "Ancient Gear Reactor Dragon". Yuri activates the effect of "Ancient Gear Gadget", letting him declare the name of another "Gadget" monster and change the name of "Ancient Gear Gadget" to that card's name until the End Phase. He declares "Red Gadget".
Yuri Tributes "Wyvern" and "Gadget" to Tribute Summon "Reactor Dragon" (3000/3000) in Attack Position. "Reactor Dragon" attacks "Natasha". As another "Cyber" monster she controls is being attacked, Alexis activates the effect of the other "Natasha", which would negate the attack, but the effect of "Reactor Dragon" prevents the opponent from activating Spell or Trap Card, and Monster Effects until the end of the Damage Step. The attack continues and "Natasha" is destroyed, with the effect of "Reactor Dragon" inflicting piercingbattle damage as it was Tribute Summoned by Tributing an "Ancient Gear" monster (Alexis: 5000 → 3000). As "Reactor Dragon" was Tribute Summoned by Tributing a "Gadget" monster, it may attack twice per Battle Phase. "Reactor Dragon" attacks and destroys the second "Natasha", inflicting piercing battle damage (Alexis: 3000 → 1000). Yuri Sets a card.
Turn 3: Alexis
Alexis activates the effect of the "Natasha" in her Graveyard, banishing another "Cyber Angel" monster from her Graveyard to Special Summon "Natasha" and take control of a monster her opponent controls. She banishes one copy of "Natasha", Special Summons the other copy (1000/1000) in Defense Position and takes control of "Reactor Dragon". Alexis activates the effect of "Natasha", increasing her Life Points by half the ATK of "Reactor Dragon" (Alexis: 1000 → 2500). Alexis begins to declare an attack, but Yuri activates his face-down "Unfinished Ancient Gear" before she can finish and allow the effect of "Reactor Dragon" to prevent the activation of cards. This lets him Special Summon an "Ancient Gear" monster from his hand in Defense Position, ignoring the Summoning conditions. That monster cannot be destroyed by battle this turn, but its ATK and DEF will be halved. He Special Summons "Ancient Gear Golem" (3000/3000 → 1500/1500).
"Reactor Dragon" attacks "Golem", which is not destroyed by battle, but piercing battle damage is inflicted (Yuri: 4000 → 2500). "Reactor Dragon" attacks "Golem" a second time (Yuri: 2500 → 1000). Alexis activates the Continuous Spell Card "Fusion Destruction" by sending a "Polymerization" in her hand to the Graveyard. This lets her look at her opponent's Deck and banish up to three "Polymerization" and/or "Fusion" Spell/Trap Cards from it, then inflict 300 damage for each one. She sends three copies of "Polymerization" (Yuri: 1000 → 100).
Turn 4: Yuri
Yuri activates "Ancient Gear Workshop", letting him add an "Ancient Gear" monster from his Graveyard to his hand. He adds "Wyvern". He Normal Summons "Wyvern" (1700/1200), whose effect activates as it was Normal or Special Summoned, letting him add a "Ancient Gear" monster from his Deck to his hand. He adds "Ancient Gear Box" and subsequently discards it to activate "Super Polymerization" to Fusion Summon a Fusion Monster from his Extra Deck, using monsters from either side of the field as Materials. Cards or effects cannot be activated in response to this card's activation, preventing Alexis from activating the effect of "Fusion Destruction", which would let her negate its actvation. Yuri fuses "Golem" and "Wyvern" from his field with "Reactor Dragon" from Alexis' field to Fusion Summon "Ultimate Ancient Gear Golem" (4400/3400) in Attack Position. "Ultimate Golem" attacks and destroys "Natasha", with the effect of "Ultimate Golem" inflicting piercing battle damage (Alexis: 2500 → 0).
When Alexis' Graveyard is shown when Special Summoning "Natasha" by its own effect "Cyber Tutubon" is shown. However, this card was returned to the deck for the Ritual Summon of the second "Natasha" during her last turn.
The following cards appeared in this episode. Cards in italics debuted here.