"I am Xehanort from the most distant past. My future self gave me a task - to visit the splintered versions of myself in many worlds and ensure they gathered here today."
—Young Xehanort to Riku
Young Xehanort, referred to as the Unknown (謎の男 Nazo no Otoko) and the Mysterious Figure in the North American, PAL, and Final Mix versions of Kingdom Hearts: Birth By Sleep, is a boss in Kingdom Hearts: Birth By Sleep and one of the main antagonists in Kingdom Hearts 3D: Dream Drop Distance.
This version of Xehanort is Xehanort as a teenager and was given the power to travel through and manipulate time itself to help his older self accomplish his goal of containing his essence in thirteen different vessels.
In Kingdom Hearts Birth By Sleep, Young Xehanort's body is completely covered by a hooded Black Coat with a fairly tall and masculine build. He never speaks at any point of the game.
In Kingdom Hearts 3D: Dream Drop Distance, he has silver hair, dark skin, an adolescent face and golden eyes.
Young Xehanort's body model is a copy of Saïx's. It may or may not have a deeper meaning as Saïx/Isa has not transformed into a full clone of Master Xehanort yet.
Young Xehanort is an incredibly powerful being. He was granted the power of space-time manipulation by Ansem, which he uses to great effect; for example, he recovered from the effect of Mickey's most powerful Stop spell far faster than any of his comrades. His power over time is such is that he can manipulate the flow of battle, performing such feats as slowing his opponent or reversing the flow of time to regenerate health. Like his older self, he is a powerful magic user, able to cast powerful Fire and Blizzard spells, teleport around the battlefield, throw Riku and Mickey with telekinesis, and fire magical bullets similar to those used by Sora's Wisdom Form.
In Kingdom Hearts Birth by Sleep, he is immune to all status effects and possesses incredible speed and agility. Additionally, he is able to duplicate himself, summon pillars of fire, use a countless number of lasers and turn himself invisible. He also has access to a plethora of the numerous protagonists' most powerful attacks, such as Meteor, Mega Flare, Raging Storm and Tornado. In Kingdom Hearts 3D: Dream Drop Distance, he can enter the World of Sleep, summon Dream Eaters, open Keyholes and the Corridors of Darkness.