Kibisis: Bag of Barrier Inversion (鏡像結界の袋, Kyōzō Kekkai no Fukuro?) is the sack used by Perseus to defeat the Gorgon Medusa and hold the demon's head after it was severed with Harpe. It is an anti-sealing Noble Phantasm that distorts the concept of the world through a mirror world-type Bounded Field that places the inside of the pouch on the outside and the outside of the pouch in the inside. It inflated and swallowed Perseus, creating a fold in space that placed the outside world into the inside of the bag, and Breaker Gorgon, which affects only what is inside, was reflected back, making Medusa look upon herself as if reflected in a mirror, allowing him to slay her with Harpe while she was immobilized.
As per legend, it contains the Gorgon's head that has been turned into Perseus's Noble Phantasm.