Game:Demyx

Demyx is fought as a boss in Kingdom Hearts II. He attacks Sora and his allies in the Underworld, as well as in Hollow Bastion during the Battle of the 1000 Heartless. He can be fought again in a data rematch in Kingdom Hearts II Final Mix.

First encounter
During the first battle, Demyx does not physically attack. Instead, he summons 100 water forms that must be defeated within eighty seconds. Water forms have two shapes, musical notes and Demyx doppelgangers. Striking the Demyx-shaped forms will cause them to transform into note-shaped ones. The note forms can be grabbed with the Reaction Command Wild Dance, which causes damage to many forms over a large area. It is recommended to use the Wild Dance Reaction Command as well as the Fire spell as many times as possible. It should be noted that the note-shaped forms will attack if left untouched for some time. Ethers should be stocked to refill the MP Gauge after a consecutive round of Fire spells, but HP should not be a problem, as defeating the water forms causes HP Balls to drop.

Second encounter

 * Attacks
 * Water Dash: Dashes forward leaving pillars of water behind and ending with a circle of pillars around him.
 * Bubble Blaster: Rapidly shoots bubbles at the enemy.
 * Bubble Drop: Drops bubbles onto the foe.
 * Form Summon: Summons water forms to fight.
 * Wall Walk: Walks toward Sora with a wall of water pillars in front of him.
 * Water Finish: After yelling, "Come on, keep to the beat!", Demyx strikes Sora with his Sitar a couple times, sending out pillars, and then ending with a blast of many pillars.
 * Pillar Cast: Casts a line of pillars that chases Sora.

When the fight begins, Demyx summons his "water forms", and Sora must destroy fifty forms in forty seconds. In addition to the Wild Dance Reaction Command, Limit commands also help to destroy the water forms quickly.

After the forms are destroyed, Demyx begins his normal attacks. He will leap across the arena with spouts of water erupting from the ground in his wake, and summon pillars of water around him. To stop him, try to hit him with a combo finisher before he leaps again. Demyx can leap and summon water even when knocked into the air by a combo, so be careful attacking him in the air. Demyx will also summon a rain of bubbles from above, and fire a bombardment of bubbles at Sora directly. He can also summon several spheres of water around himself, which explode after a short delay. Demyx will often summon two or three note-shaped water forms as back-up during the battle, and while there is no timer, these water forms will attack Sora and can cause heavy damage, although Sora can use the reaction command to destroy them and cause collateral damage to Demyx.

Sora may occasionally get the chance to use the Show Stealer command—signaled by Demyx marching toward Sora while playing his sitar and quipping "Ain't it a blast?"—which knocks Demyx into the air and stuns him for a short time. This can backfire, however, as approaching Demyx without triggering the Show Stealer will result in Demyx automatically counterattacking with his sitar and doing major damage.

When he has lost approximately half his health, Demyx will summon ten more water forms that must be defeated in ten seconds, fifteen seconds in the Final Mix version. Afterwards, Demyx resumes his normal attacks, but also gains a new technique, Water Finish. He will walk towards Sora, swinging his sitar, summoning walls of water in front of him and behind of Sora. If Sora uses Guard against Demyx's sitar, he can sometimes avoid being damaged by the pillars, allowing him to counterattack.

Most of Demyx's attacks knock Sora into the air, so Aerial Recovery is very useful. It is highly advised to stay away from Demyx until he is open for an attack. For this reason, Thunder helps greatly, and Wisdom Form is also useful.

An alternate method is to beat all the water forms in the beginning and immediately use Knocksmash. The "Duo Raid" portion knocks Demyx into the air and prevents him from using any attacks. The "Cosmo Boost" portion deals more damage as Goofy flies around hitting him. This combo takes his health down almost completely for an extremely easy win, without using any other magic or Drive forms.

Data Rematch
Demyx fights in a similar manner to the previous battle, but this time he makes use of more water forms. There are four rounds of water forms at the start, and Sora must destroy all of them in thirty seconds without using the "Wild Dance" Reaction Command. The final round has 99 forms, when Demyx has one bar of HP left. Also, Demyx's fountains increase in number and power and some briefly follow Sora, which somewhat resembles Vexen's Ice Needles Sleight.

It is advisable to stock up on Ethers/Elixirs or any MP-restoring items in the item slots, including Donald and Goofy's, and have Donald and Goofy carry out their attacks very frequently. Disable any Auto-Limit support abilities, as this might prevent usage of the Reaction Command "Wild Dance" and might force one into Limit mode instead, making it more difficult to destroy all the forms in time. The note-shaped water forms do not appear, but casting Blizzaga on the forms will turn them into notes and allows the use of "Wild Dance". Firaga will also instantly destroy the water forms. Switch to Limit Form and use Ragnarok.

Alternatively, switch to Wisdom Form and use magic-based attacks. Reflect and Fire will come in handy—as while in Wisdom Form, casting magic is done at a faster rate and Sora can move around quicker.

Also, be sure to reset the Anti-Points counter to zero before the battle, so as to help prevent Sora from entering AntiForm. However, one attack from AntiForm can destroy a form, but is not recommended.

Heal when necessary, but prioritize MP for attacks.