The Celestial Robe (天女の羽衣, Tennyo no hagoromo, "Feathered Robe of the Celestial Maiden") is the most powerful and essential of Kaguya's paraphernalia. Originally belonging to the real celestial maiden, the robe acts as a source of infinite power for Kaguya and greatly strengthens her abilities. In addition to giving her unlimited power, its healing abilities also allow Kaguya to instantly recuperate from any injury. Kaguya's primary purpose for the Celestial Robe, however is in its function as an energy source, for which she uses to power her Mirror of Stillness spell and put a permanent halt to flow of time.
While originally in Kaguya's possession following her absorption of the real celestial maiden, it was stolen by an unknown passerby while Kaguya was bathing in a spring. Without its power, Kaguya became vulnerable and was sealed away by the monk Miyatsu. The Robe eventually fell into the hands of the Hōjō clan, who were warned by Miyatsu that if ever a full moon should appear for several consecutive nights (indicating Kaguya's awakening) that they should throw the Celestial Robe into the crater of Mount Fuji. This would essentially prevent Kaguya from initiating her plan to stop the flow of time. While a young samurai from the Hōjō clan, Akitoki Hōjō, attempted to destroy the Celestial Robe, he was waylaid en route to Mount Fuji by Kaguya, who then took possession of the Robe. After Kaguya's defeat, however, Akitoki threw the Robe into the crater of Mount Fuji to ensure that its power could never be used for evil purposes again.
Kaguya spoke this verse when attempting to claim the robe:
The time has now come. Behold the robe from heaven to drape upon my shoulders. And for it, it is but a deep sadness that I feel.
Ima wa tote Ama no hagoromo kiru ori zo, kimi o aware to omoi ide keru
- The Celestial Robe is based on the one in The Tale of the Bamboo Cutter (竹取物語, "Taketori Monogatari").