After Sora locks the Hollow Bastion Keyhole, a hidden boss is opened up at the Neverland Clock. To find the boss, return to Neverland and disembark in the Ship: Cabin Are. Put Peter pan in your party and and speak to Tinker Bell in the Corner of the Room.

Preparations:

Fill Sora’s Item Slots with Ethers and Elixirs, and maybe a few Mega-Potions. Make sure his quick magic has Fire, Thunder and Blizzard Magic. Your Party should Include Sora, Peter pan and Goofy, and all of them should be equipped with MP Gift Ability.

Phantom
1200 HP — 9999 EXP

This boss battle is extremely difficult as if you don’t watch the clock hands, you could soon find your self alone! Eventually, one of your characters will get banished but don’t worry about it, as he has helped as much as he could. As soon as the battle begins, lock onto the clock hands of any side of the tower and cast Stop. If you don’t, then the Phantom will cast Oblivion on one of your Characters. When the Spell on the stop wears off, Recast it immediately, or one of your Characters will be sentenced to Oblivion, never to be awakened again (Until the battle is over).

The Phantom is Invulnerable until a little orb beneath it shows up. The Orb shows the Phantoms Weakness, which are listed below.

Orb is White – Attack with Physical Attacks
Orb is Red – Attack with Fire Magic
Orb is Blue – Attack with Blizzard Magic
Orb is Yellow – Attack with Lightning Magic

Only use Items to heal Sora, as you need the MP for casting Magic. For Defeating the Phantom, Sora’s Stop Magic is Upgraded.