Conformer (不倶戴天, Fugutaiten?, lit. Quarrelsome Even Under The Same Heavens, Irreconcilable Vengeance) is a recurring weapon in the series. It originally appeared as Yuffie Kisaragi's ultimate weapon from Final Fantasy VII.
The Conformer is Yuffie's ultimate weapon, found in the Gelnika. It provides 96 Attack, 112 Atk%, 42 Magic, and 4 double Materia slots with Nothing growth. It has a unique mechanic where it deals more damage the higher the enemy's level is. It holds unique properties; when using the Morph command with it, damage is not reduced, making it the best way to farm items. When used against allies, it will always deal 1 HP of damage, but there is no attack sound and no damage numbers are displayed.
The Conformer derives its original name from a yojijukugo proverb adopted from the Chinese Book of Rites, which is heralded as one of the Five Classics of Chinese literature, and an instrumental Confucian guideline that was adopted in early Japan. It is taken from verse 2 of Chapter 5 of the first book: "With the enemy who has slain his father, one should not live under the same heaven. With the enemy who has slain his brother, one should never have his sword to seek (to deal vengeance). With the enemy who has slain his intimate friend, one should not live in the same state (without seeking to slay him)." Ultimately, it is a maxim detailing retribution and revenge for loved ones.