The No Heart is a boss exclusive to Kingdom Hearts Birth by Sleep Final Mix. It is a data simulation of Master Xehanort in his Keyblade Armor, and is fought within the "Foresight unto Darkness" battle in the Mirage Arena. It wields Master Xehanort's Keyblade in battle. At the beginning of the battle, it sits on a throne in the Throne Room of the Land of Departure, and it later stands up to fight the character directly.
- No Heart summons a horde of flying keyblades to attack the character.
- No Heart uses a Corridor of Darkness that absorbs and traps the character on the barrier.
- No Heart utilizes the Dark Volley Shotlock, which consists of launching multiple dark projectiles at the character.
- No Heart utilizes Sonic Impact, darting around the arena to attack the character.
- No Heart creates waves of dark energy by swinging its Keyblade.
- No Heart leaps into the airs and slams the ground, creating a large shockwave.
- No Heart utilizes Reversal to trick the characters and strike with the Keyblade several times.
- No Heart creates pools of dark energy that can slow down the character, speed up its projectiles, and even bind the characters, preventing them to move aside.
- No Heart morphs its Keyblade for strong attacks, like turning it into a claw, a power up for its kicks, and even a wing to be able to fly.
- No Heart creates a large explosion of dark energy that will instantly drain all HP, Commands, the focus gauge, and leave the character stunned.
- No Heart telekinetically commands its Keyblade to attack characters and absorb any damage directed to it.
No Heart is one of the strongest secret bosses in the game. Its attacks are strong and can deal heavy damage. In terms of preparation, the character should be at a high level, have a strong Keyblade, max HP, and lots of Cure and Potion commands, as well as have the Second Chance and Once More abilities equipped.
In the first phase of the battle, No Heart remains stationary, protected by a large barrier of dark energy. To disable the barrier, the character must attack No Heart's Keyblade, which is constantly floating around. In terms of offense, No Heart will summon a swarm of flying Keyblades from the Keyblade Graveyard that can be Blocked, or even destroyed by commands such a Raging Storm, to attack the character. It occasionally uses an advanced Corridor of Darkness which absorbs and traps characters on the barrier (Template:Button must be pressed repeatedly to break free), and may use Dark Volley. The boss's Keyblade is vulnerable to any attack. After dispelling the barrier, the fight becomes more serious as No Heart rises from the throne, removes its cape and challenges the character directly.
This is the harder phase of the battle. The boss possesses an arsenal of potent dark-based attacks which can deal large, and possibly fatal damage. No Heart mainly uses Sonic Impact, darting around the arena to attack the character. The boss can utilize Dark Volley to strike from a distance, as well as summon flying Keyblades to attack. The boss can create waves of dark energy by swinging its Keyblade. It may also leap into the air and slam the ground to create a large shockwave.
No Heart can use Reversal to maneuver around the character to unleash more Keyblade strikes, and may completely block attacks with its Keyblade. No Heart also can create large pools of dark energy that will either slow down or speed up anything that is inside, including its projectiles, and may even bind the characters in place with no means to move aside.
The armor can also alter the shape of its Keyblade for strong attacks (a similar fighting style to the Lingering Will) such as turning it into a claw to grab characters (Template:Button must be pressed repeatedly to break its grip), a spinning duel edge blade, a gun that can shoot powerful shots, morphing it around its leg for powerful kicks, and turning it into a wing to fly.
From the air, it will either shoot more dark energy blasts, summon more flying Keyblades to attack, dive at the hero repeatedly, or use its most powerful attack: A large explosion of dark energy that will instantly drain all HP, Commands, the focus gauge, and may leave the player stunned if characters are in the vicinity. It may also telekinetically command its Keyblade to attack characters directly and to absorb any damage directed to it.
The reward for defeating No Heart is the Crown Unlimit Keyblade.