The Master of Masters

The "Master of Masters" is a Keyblade Master that appears Kingdom Hearts χ. He is responsible for creating the Book of Prophecies using his gift of foresight, as well as for training his apprentices Luxu, Ava, Gula, Invi, Aced, and Ira.

Before Kingdom Hearts χ
According to the 's Chirithy, the five Foretellers and one other Keyblade wielder were the apprentices of his creator, the "Master of Masters". Shortly before he disappeared, the Master of Masters assigned his disciples new names and gifted five of them with a tome from the Book of Prophecies, which taught them of the event that would doom the world.

Kingdom Hearts χ
After helping Chirithy fend off the Minute Bombs in Daybreak Town, the Player goes to sleep and has a dream in which the five Foretellers are conversing with their master. Before the Player has a chance to approach the Foretellers and their mysterious visitor, they are engulfed in darkness and wake up.

Later, when the Player has another dream of Ephemer entering the clock tower through the sewers, the Master of Masters can be seen watching him from the shadows.

Appearance
The Master of Masters conceals himself in a black coat. His eyes, one of which he has placed in Master Xehanort's Keyblade, are blue with catlike pupils.

Abilities
The Master wields a Keyblade that lacks a name in his own era. It has a dark black handle with a raised spiral carved around it. Its pommel and guard resemble black, demonic wings. The base of the blade is an etching of a horned lion, and the shaft is formed from two black, barbed blades, etched with a white icon resembling a bramble of thorns. The teeth are formed in the shape of a demonic wing, and are set with an eye of darkness. The Keychain is made of small, grey links, and the token is an entangled, grey talisman with an eye of darkness. Unlike the Keyblades of the apprentices, it lacks Terra's Mark, and instead holds the Master's own "Gazing Eye", granting him precognition of all the events the Keyblade will witness throughout time.