The Master of Masters

The "Master of the Masters" is a hooded character introduced in Kingdom Hearts χ. The Unknown's true identity and purpose remain unknown.

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

Appearance
The Unknown appears as a person completely concealed in a black coat. Nothing else is known about the unknown's appearance beneath the hood.