Prison Keeper

The Prison Keeper is a Heartless boss in Kingdom Hearts II. It appears in Halloween Town on the first visit.

After Maleficent resurrects Oogie Boogie, she left Lock, Shock and Barrel behind to deal with Sora and Jack Skellington. She summons a Heartless called the Prison Keeper. Lock, Shock and Barrel sit in the cage at its base.

Strategy
Equip all of your aerial abilities, and maybe the Hero's Crest (unless you want something with better magic.)

After a while it swallows one of the three, and its attacks depend on the child:
 * Shock: The Prison Keeper will spin its arms around, rising up and then falling down while spinning around the arena, firing lasers. Its arms glow a dark yellow. This is easy to avoid, just get close and attack.
 * Lock: It will shoot large fireballs out of its mouth and hands from a distance. These fireballs can be deflected to damage this Heartless. Its arms glow red. The best way to counter this is to knock them back.  Reflect Magic, although useful, is not recommended.  Save MP by simply using the block ability.
 * Barrel: It will use a powerful biting attack on just Sora and slash madly. Its arms glow green. Keep your distance and use Thunder.

Near the end of the fight, it swallowed all three and used a mixture of attacks: it shot fireballs from its eyes, slashed, and spun. Don't even get near it now. Instead, use wisdom form, keep your distance, and continue strafing (don't stop moving) until it is defeated. Donald's Limit is also helpful here.

Sora defeated the Heartless and Lock, Shock and Barrel reveal Maleficent's plot.

Kingdom Hearts II
A Heartless called forth in Halloween Town by Maleficent to get revenge on Sora.

It held Lock, Shock, and Barrel captive while dealing various elemental attacks.

Trivia

 * The Prison Keeper is the only Heartless boss ever to appear in Halloween Town in the series, except for Chimera in Kingdom Hearts: Final Mix.
 * The Prison Keeper is the first boss to have over 1,000 health in Kingdom Hearts II.
 * The Prison keeper is the only other boss, the first being the Pot Centipede, to have no cutscene showing its demise.
 * Oddly enough, if you don't visit Halloween Town until the second half of the game the Prison Keeper will have more health than every other boss you have to defeat to complete the game.
 * In Kingdom Hearts Final Mix+ the Prison Keeper's hands glow a spooky green.