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.

Personality
The Master of Masters is rarely serious, often making goofy movements and actions. With his gift of prophecy, he knows what will happen, and has taken a carefree look to the impending Keyblade War. He entrusts Luxu with a Keyblade with his Gazing Eye in it, so that he can see the future as the blade is handed down; this shows the Master of Masters is curious about how the world will be once the war is over. He wrote down events of the future in five books, which became the Books of Prophecies, showing that he didn't mind giving a sneak peek at what was to come. However, there was one secret he kept, which was what the contents of a secret chest were; he told Luxu, telling him never to open it.