Phantom

Phantom is an optional boss from Kingdom Hearts. He was one of the powerful Heartless released by after the Hollow Bastion Keyhole is sealed, and can be found in Neverland at the Clock Tower. While Phantom is in possession of the Clock Tower, the treasures that are normally released every hour are temporarily halted until his defeat. He was one of the hardest bosses to defeat in Kingdom Hearts and Kingdom Hearts: Final Mix, matched only by Kurt Zisa and Sephiroth.

This powerful Heartless haunts the Clock Tower until Sora is sent by Tinker Bell to stop him. Phantom has a few attacks, including a simple slash and a spell that sends out a puff of darkness to drain Sora's health. His main defense is to hide his weak point. When Sora defeats Phantom, he fades into the town and grants Sora a Stop magic upgrade.

When his heart disappears, he is invulnerable.

Journal Entry
''Ghostlike Heartless Who haunted the clock tower standing far away from Neverland. Fluttering his eerie cloak, he cast a spell to take Sora's heart. Having no physical body, regular attacks were useless, but in the end Sora and company discovered his weakness and prevailed.''

Abilities
Phantom's main ability is the fact that he's completely invulnerable when his heart is not showing. This can make it hard to deal damage to him quick enough to prevent him from activating his second power.

Phantom will occasionally start the hands on the Clock Tower, and will start a 'Countdown Curse'. As the curse cannot be lifted, Sora's allies will be eliminated from the battle, one by one, ending finally with Sora. This process can be slowed simply by casting "Stop" on the clock hands. Party members killed in this way can't be healed or revived.

Phantom can also use a second curse, by which he summons a small ball of energy which spirals after Sora, dealing damage on up to five separate occasions. This spell can be avoided, however, by hiding around a corner of the Clock Tower, or it can be neutralized by casting Aeroga on Sora.

Phantom can also preform a short-range, very damaging slashing combo with his claws, however this is not as dangerous as his other attack.

Weakness
Phantom's weakness is his heart. He guards it fiercely, only revealing it every now and then. Once his heart is exposed, it will be one of four colors. Depending on the color, a specific attack must target it:
 * White color - Physical attack
 * Red color - Fire
 * Blue color - Blizzard
 * Yellow color - Thunder