Phantom

Phantom is an optional boss from Kingdom Hearts. It 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 the Phantom is in possession of the Clock Tower, the treasures that are normally released every hour are temporarily halted until its defeat. It 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 it. The Phantom has a few attacks, including a simple slash and a spell that sends out a puff of darkness to drain Sora's health. Its main defense is to hide its weak point. When Sora defeats the Phantom, it fades into the town and grants Sora a Stop magic upgrade.

When his heart disappears, he is invulnerable.

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

Weakness
The Phantom's weakness is it's heart. It guards it fiercely, only revealing it every now and then. Once it's 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

The Phantom will also occasionally start the hands on the Clock Tower, and will start a countdown. If the countdown is not stopped, Sora's allies will be eliminated from the battle, one by one, ending finally with Sora. This can be halted simply by casting "Stop" at the clock hands