Instructions
Collect the three items in the chests in the first area of the Keyblade Graveyard, called Seat of War. One chest holds a map, which is helpful if you get lost.
Walk straight ahead to the next area, Twister Trench. Battle the enemies inside the small tornadoes if you get caught inside one. There are a few more chests here containing useful items.
Go north to the Fissue. Save your game at the save point. Head into the next area to trigger the final boss battle with Xehanort and Vanitas.
Hit the "X" button to attack both foes whenever they stop trying to attack you. Heal yourself with a potion or spell if necessary. The battle ends when you have decreased both enemy's health bars by half. At this point, a new battle begins.
Run away as soon as you see Xehanort beginning an attack, then charge back in to attack him a few times. After his health bar is depleted, Xehanort changes into a younger, more powerful version of himself.
Dodge any attacks Xehanort sends your way and hit "Square" to block his projectile attacks. If you block an attack in time, it's sent back to Xehanort, damaging him. Continue dodging and attacking until his health meter is empty.