Players of Final Fantasy Resonance can transform low‑level ancient items into powerful gear by defeating specific bosses in the Chamber of Arms, a temple located north of Dirnado and east of Gronoa. After obtaining the airship in Chapter 5, the game’s map expands enough for explorers to reach the area, where pedestals display various ancient weapons and armor. Each upgrade requires defeating a level‑50 boss that shifts into a second form once its first health bar depletes; players are advised to save their progress and adjust their Visions before engaging.

The game hides many of these ancient pieces throughout its narrative. Some are awarded as quest rewards, such as the Ancient Bow, which Fina receives after completing the "Secrets Unearthed" side quest and speaking with Chloe in Felicitas' shop. Others, like the Ancient Hammer, become available after upgrading the airship’s scanner with a Resonance Stone found in Mt. Reizan. Certain items, including the Ancient Tome and Ancient Firearm, must be purchased from a wandering merchant ship, while the Ancient Rod requires a Cabin Key obtained from a villager outside an inn in Sian.

Additional ancient gear includes the Ancient Greatsword, Ancient Katana, Ancient Whip, Ancient Cuirass, Ancient Cloak, and various accessories. Their effects range from boosting physical and magical attack stats to enhancing critical hit rates, stagger power, and MP efficiency. Some pieces, such as the Ancient Cuirass, are granted as rewards from Colosseum battles, while others, like the Ancient Garment, require scanning a specific location after acquiring a Magi‑tenna from a hooded NPC in Gaberada. The locations and acquisition methods are documented in the game’s guide, which also notes that some items may only appear after progressing further in the story.