"Behold. These lifeless keys used to be full of power. United with the hearts of their masters. On this barren soil, Keyblades of Light and Dark were locked in combat as a great Keyblade War raged!"
Xehanort is the main antagonist of the Kingdom Hearts series, and an awful old goat bent on the destruction of the universe.
Powers and Abilities
All forms of Xehanort are skilled with the keyblade. Master Xehanort, in particular, is surprisingly agile in his old age, and also has the ability to cast a wide variety of dark spells.
Young Xehanort alone has some skill with time and time travel.
Master Xehanort is very, very old. Like a billion years old or something. He most likely has to use about a gallon of Botox every month. His posture looks like he had his spine replaced with that of a monkey's or something. And he's got a stupid little beard.
You might or might not notice that he looks a bit like bald Spock. This is because the part was literally written for Leonard Nimoy, who voiced him in the KH series.
Terra-Xehanort, AKA Terranort, looks exactly like Terra, minus the terrifying fact that his eyes have turned yellow and he's started bleaching his hair as a result of Xehanort possessing him. Most incarnations of Xehanort look like Terranort, with a few minor differences, such as Xemnas's long hair, Ansem (Seeker of Darkness)'s bad tan, or Young Xehanort's bad dress sense.
LOTM: The New Multi-Universal War
Legends of the Multi-Universe: Armageddon
Xehanort was shown in the fifth memory of Myotismon. He had pleaded with Myotismon to leave the Souls of Darkness be, but Myotismon would not listen. He then killed Xehanort...with evil, sick joy!