Master Xehanort appears as a boss in Kingdom Hearts Birth by Sleep and Kingdom Hearts Birth by Sleep Final Mix. In Terra's story, he is fought twice in a row. The first fight is against both Master Xehanort and Vanitas, but the fight is ended prematurely, and the second fight is the penultimate fight of Terra's story: a one-on-one duel between Terra and Master Xehanort.
Terra will fight both Master Xehanort and Vanitas two-on-one. Vanitas should be the primary target as Xehanort will mostly dodge and keep a distance from Terra. In combat, Xehanort will periodically teleport in front of Terra and perform quick combos before launching an ice spell that can freeze him. Xehanort isn't very difficult, for after sustaining minor damage, the battle will end.
The second battle is the true battle against Master Xehanort. Like the previous battle, Xehanort will keep a distance, but will launch wide-ranged magic spells. Master Xehanort utilizes the quick combo and ice spell from the previous battle but can now also fire the ice spell without the combo, in addition with a powerful overhead thunder spell. Master Xehanort can cast a powerful earth spell, causing a huge piece of land to rise under Terra, lifting him upward and damaging him.
All of his attacks, including magic-based ones, can be dodged with the right timing; but the real danger comes from his summoning a number of Keyblades in a flowing spiral and his teleport combo. The former, while relatively easy to avoid, will deal massive damage if hit by it. The latter attack however is more difficult to predict - when the player attacks Xehanort, he can simply teleport away and attack with magic. After landing a successful combo, Master Xehanort will hold Terra onto the ground by the shoulder, at which point must be pressed repeatedly in order to be freed.
Note that failure to do so will allow Master Xehanort to attack with a powerful Blizzard spell. On rare occasions, he will teleport directly behind the player and continually attack with warping Keyblade combos. The fight can be made much easier with the use of Cure commands and Shotlocks.
During this battle, if you are defeated, when the Game Over screen is displayed, you will hear Master Xehanort saying "I could die of laughter!"
|Master Xehanort I (Kingdom Hearts Birth by Sleep: Terra)||Master Xehanort II (Kingdom Hearts Birth by Sleep: Terra)|