Xemnas

Xemnas, the Superior of the In-Between (狭間の指導者 Hazama no Shidōsha), is the Nobody of Terra-Xehanort. He was Number I in Organization XIII, the group's founder and Superior, and he is one of the Thirteen Seekers of Darkness. With power over nothingness, which he channels into the Ethereal Blades he wields, Xemnas once commanded the Sorcerer Nobodies.

Kingdom Hearts
A mysterious figure who appeared in Hollow Bastion.

Opening
No. I XEMNAS

''Organization XIII's leader. Through power over nothing, he seeks power over everything.''

Weapon: Ethereal Blades

Kingdom Hearts HD I.5 ReMIX
''Organization XIII's leader. He has made completing Kingdom Hearts the Organization's goal, but harbors his own secret agenda.''

First Entry
Organization XIII's Number I. He directs the group as its leader.

''Organization XIII is a unique presence among the Nobodies. They think and plan, and seem to have a greater goal.''

What that is remains to be seen, but they appear to know a bit about the Keyblade.

Second Entry
Organization XIII's Number I. He directs the group as its leader.

''In truth, he is the Nobody of Xehanort, who was apprenticed to Ansem the Wise. In secret, Xehanort studied the doors and the heart of all worlds, ultimately stealing his master's name, Ansem. When Xehanort became a Heartless, his Nobody Xemnas came into being.''

Xemnas is using Sora, collecting the hearts released every time a Heartless falls to his Keyblade.

Third Entry
''Organization XIII's Number I, who acts as leader of the group. Xemnas is the Nobody of Ansem's apprentice Xehanort.''

He used Sora and his Keyblade to collect hearts from the Heartless and see Kingdom Hearts to its completion.

Kingdom Hearts 3D: Dream Drop Distance
''Xehanort's Nobody, who was once leader of Organization XIII. He tried to create Kingdom Hearts from the hearts of people, but Sora put an end to his plans and the man himself.''

So why is Sora seeing him now?