Roxas discovers Captain Hook and Mr. Smee taking a captive Tinker Bell back to their ship. He follows them, and learns that Hook has been following fake treasure maps in the hopes of finding a real one among them. Hook tears up one of the fakes, and he and Smee leave the ship to continue their hunt. Roxas frees Tinker Bell, and follows one of the pieces of the torn map, expecting to find a Heartless.
When no Heartless appears, he tracks down Hook and Smee, who are digging up another chest. Hook's greed ends up summoning a Phantomtail. Roxas slays this monster, and returns to the Castle That Never Was. After he leaves, Pete comes by the dig site, wondering what happened to the Heartless he had expected Hook to attract. Pete realizes someone is destroying the Heartless, and plans to summon an enormous Heartless.
At the start of the battle, Lock-On to the Phantomtail's wings or tail as it hovers above you. As this is an aerial battle, you must jump to the Heartless's level before you can begin your attack. Use caution, as the boss will eventually proceed to summon homing balls of blue energy to damage you. From this point forward, the Heartless will warp around the battlefield each time a hit lands to its head, making attacks difficult.
You must also be careful not to get too close to the Phantomtail, as it will stab you with its talons in an attempt to knock you away. Another attack in this Heartless boss's arsenal involves it spiraling into you, dealing impact damage. The Phantomtail will also flip in the air, damaging those in its way. So long as you heal periodically, utilize your Limit Break, and attack whenever possible while at the same time dodge the Heartless's attacks to the best of your ability, you should be able to tackle the Phantomtail in a matter of minutes. If you wish to use Magic in this battle, use it when the Heartless is stationary. Attempt a spell while the beast warps to a new location, and your spell is guaranteed to miss.
Another strategy is to continue hitting the Phantomtail's head. Though it may teleport away, if you can keep up, you can still continue to deal damage, and it will not be able to counter. If, however, it does gain the upper hand by avoiding your attacks, simply fly far away until it ceases attack. If it fires its homing energy balls at you, fly away, they will fizzle out eventually. Also, if you have Thundaga equipped, wait until right after it ceases its spin or flip attacks, then let it rip!
A Phantomtail is a large, draconian creature with predominantly pink skin, save for its shoulders and legs, which are black. Its body is rather thin, while its feet are quite large and have a peculiar shape, each one consisting of only two black claws; a large front one and a small rear one. The Phantomtail's tail is long and ends in a large, bent hook. Its wingtips end in small hooks. Its head sports two short horns above each of its eyes that point forward. It has beady yellow eyes on either side of its head, and its Heartless emblem is on its chest.
The former part of the Phantomtail's name is a reference to its eerie, ghost-like appearance, while the latter part highlights the size of the Heartless's tail.