The Master of Masters, also known simply as the Master, is a Keyblade Master who appears in Kingdom Hearts χ. Gifted with the power of foresight, he writes the Book of Prophecies and trains six apprentices: Ira, Aced, Invi, Gula, Ava, and Luxu.

Knowing he will soon disappear from the world, the Master of Masters gives new names to his six apprentices. He also bestows a copy of his Book of Prophecies upon five of them and assigns a unique role to each.

The Master of Masters behaves in an unpredictable and eccentric manner. He is a mischievous and playful individual, appearing curious about what will become of the world after the Keyblade War, in spite of already knowing the answer. Although he demonstrates a more serious side to his persona, especially when talking about the specific roles he had given to the Foretellers, he has a tendency to weave in and out of serious moments at a mere whim, being somber at one moment and laughing playfully the next.

He is immensely intelligent, as he is able to create new entities such as the Chirithy.

(Source: Kingdom Hearts Wiki)