Lingering Will

The Lingering Sentiment (留まりし思念) is an unlockable secret boss featured in Kingdom Hearts II Final Mix. It only appears after the player has completed every world and has defeated Xemnas. If these conditions are met, a large portal opens in the Hall of the Cornerstone, in Disney Castle. It later appears briefly as a playable character at the climax of Kingdom Hearts Birth by Sleep.

Kingdom Hearts Birth by Sleep
After Master Xehanort possesses Terra and becomes Xehanort, his feelings toward Ventus and Aqua, and his hatred toward Master Xehanort find residence in his discarded armor, forming the Lingering Sentiment. The Lingering Sentiment defeats Xehanort, leaving him unconscious. The armored figure sticks its Keyblade into the ground and kneels down (in the same position it is in when Sora finds it eleven years later). Suddenly, a sphere of light, formed by the shattered X-Blade, consumes Xehanort. The dark clouds return to their original positions as Kingdom Hearts disappears, and the Lingering Sentiment remains alone in the Keyblade Graveyard, promising to Aqua and Ven that someday, somehow, it will put an end to the conflict.

Kingdom Hearts II Final Mix
After the defeat of Xemnas, a portal to the Keyblade Graveyard appears in Disney Castle. Sora, Donald, and Goofy enter the portal and find the Lingering Sentiment, which at first mentions Aqua and Ventus and mistakes Sora as "the one he has chosen" (revealed in Kingdom Hearts Birth by Sleep to be Riku), then wonders if Sora is Xehanort before finally attacking him. Sora manages to defeat the Lingering Sentiment after an intense battle, and the Lingering Sentiment respectfully acknowledges Sora as a true Keyblade Master. If Sora comes back for another match, the Sentiment accepts, but states that he has nothing left to give him and that all he has left is his hatred for Xehanort.

In the game, the Sentiment speaks to Sora through enigmatic sounds, much like Xemnas does in Kingdom Hearts Final Mix, yet Sora appears to be capable of understanding it, demonstrated by when he, Donald and Goofy immediately take fighting stances when the Sentiment mentions Xehanort. Kingdom Hearts: Birth by Sleep, however, reveals that the Sentiment is fully capable of human speech despite being a heart inside armour, having the same voice as Terra.

Journal Entry
A man connected to the portal﻿ which appeared at Disney Castle.

The armor covering his body can master the Keyblade's power much more than Sora.

Fighting Style
It, like the game's other secret bosses, is difficult to defeat; its most basic moves are attacking with its Keyblade Gaia Bane (using a combo attack almost identical to Sora's, except that at the end it turns its Keyblade into a drill-like object for the forward thrust), and can fly at very high speeds. Its main abilities are transforming its Keyblade into various attacking forms. It can turn it into a whip that does less damage than the blade form, but its greater speed and reach makes up for it (it's so fast that if Sora is hit by it he won't be able to dodge or block the other hits), or a massive cannon (which is even bigger then the Lingering Sentiment itself) that fires out a large, very powerful ball of energy (Sora, however, can deflect this back to the Lingering Sentiment, which leaves it very vulnerable), a jet-ski like object that lets it fly extremely fast, a cog-like object that spins around so fast that if Sora gets hit by it once, then the rest of the hits will also hit Sora. It can also conjure a "ritual" like attack, which undergoes into a berserker-like condition (similar to Saïx's Berserk Technique) in this form, its arm gauntlets and helmet will emit a bright red, which he can split its Keyblade into two weapons. This, when added with its combos, makes it extremely lethal. It's only vulnerable after completing an attack or after deflecting the cannon shot back at him (as mentioned above). Any other time that you attack him will do nothing at all.

In addition to its Keyblade, the Lingering Sentiment has other abilities as well. It can also create an unusual looking seal that either creates an orange or blue orb. An orange orb causes Sora to be unable to attack and a blue orb prevents Sora from using magic or items. It can also conjure drone-like objects which fire plasma at Sora and his party. A particularly deadly attack is trapping Sora in a triangle of objects that drain his heath at a very fast rate (similar to an attack used by Xemnas, but much more powerful), and only a "Break Free" command on Sora command list can save him from it. If the player chooses the wrong command while he is trapped, then Sora will immediately die (even with Once More and Second Chance equipped). Interestingly, when it strikes Sora with its Keyblade(s), most of its combos resembles Sora's combos, most notably the Valor and Final Form combos.

Strategy
Basically, all you would have to do is to dodge the Sentiment's attacks by using Dodge Roll or Guard, specifically for when he swings his Keyblade around or turns into the jet-ski like object. When starting to attack the Lingering Sentiment, the attacks will be an insignificant amount of damage and the only way to stop this effect is to land a combo on it and damage it takes will be normal. It will mostly use the whip technique after it has been hurt badly a few times, particularly by a powerful finishing move, so use the Quick Run to avoid this after striking him hard twice. If he transforms into the floating guns, just deactivate Lock-On and fly as far away as possible, and turn around stone pillars to make the guns destroy themselves. For the cannon, just deflect the bomb back at it using Guard, and if it isn't possible, just Dodge Roll through it (it will explode without hurting Sora, but be careful with Donald and Goofy). Once it goes into the berserk state, Guard as much as possible and when it strikes the ground, fly for it. Once it gets ready to strike again, cast Reflect as much as possible until it's attack finishes, where you should strike him with thunder to leave him vulnerable to a good retaliation.

Make sure to load yourself, Donald and Goofy with ethers in case the Sentiment casts the spell on you which stops you using Magic. Be extremely careful when he gets ready to trap you in the energy-draining triangle. A good indication is when his Keyblade makes a gun-loading noise. Once you hear it, get ready to Dodge Roll at a specific timing rate to avoid the beam hitting you. At the start of the battle, he will shoot three times, but later on, four, so be on the lookout. After the last shot, strike him hard.

At times, the Sentiment will start running towards you. If you are too far away, he will jump towards you and maybe land near you, giving you a striking chance. If he is running near you, he will either use a basic but powerful Keyblade move that ends in a drill of energy, similar to Sora's Guard Break, or he will through his Keyblade into the ground and create a vortex of energy that if it hits Sora, it will take away his ability to either attack or use magic. A small lifebar will appear for the Sentiment and you will have to drain this in order to regain the lost ability. The best magic to use is either Fire or Thunder, but be sure to equip only one of these with Reflect and Cure. If you can't use magic, be extremely careful, as you will not be able to heal yourself. To avoid the drill, just stay in the air above the Sentiment and hit him once he puts it away. In the case of the vortex, be sure to observe him and either use Dodge Roll or Reflect at the precise moment, and you will escape, but do not try to hit him, as he will still be invulnerable.

Watch out for lethal combinations, though, such as him trapping you in the triangle or, going into the berserk state while you can't Attack or use Magic; or him summoning two guns to aid him while he flies around on the jet-ski. If you have Once More and Second Chance equipped and you get hit by one of these combinations, just let him keep hitting you while you're in the air, the last bit of energy will stay with you. Once it's over, heal yourself if you can.

Despite being the weakest, the recommended Keyblade is the Kingdom Key, given you are at level 99. You can use Fenrir or Rumbling Rose if you please, but Fenrir has the disadvantage of Negative Combo and Rumbling Rose has the Finishing Plus, which will make the Sentiment angry quite quickly and force him to use the whip attack when Sora is not ready to guard. Oblivion would be quite useful as well, but as the Kingdom Key is the weakest, it will take the Sentiment most time to get angry. At first, striking him takes little health away, but gradually, the longer the combo, the more health he will lose and the more powerful the finishing move will be.

Occasionally, in times of desperation, you can quickly use Limit Form to regenerate your health and MP if you are almost out of both and Donald and Goofy are out cold, but be careful to do it in the right place, as the Sentiment may unleash an attack that will hurt you immediately after you transform, or you might be sent into Anti-Form. If possible, go into Final Form at the start of the battle and immediately revert back once you have the chance. It wastes Drive bars, but it's a 100% guarantee that you won't go into Anti-Form when trying Limit Form. Do not try to use any special Limit Form moves on the Sentiment, as they will do him little damage. Whenever curing yourself, try to be as close to Donald and Goofy as possible so they can use their ethers on you.

Stick to these rules and observe the Sentiment very carefully, and you should be able to beat him. The Lingering Sentiment is by far the hardest boss in Kingdom Hearts II Final Mix and was arguably one of the hardest bosses in the series, having no real match until Vanitas's Sentiment in Kingdom Hearts Birth by Sleep.

Quotes

 * Aqua... Ven... Keyblade... Who are you? I can feel it - we have met before. But when... No... it isn't you... It isn't you that I have chosen. Why isn't it him? Xe...ha...nort... Is that you? Xeha...nort... Xehanort!
 * I see. Your strength is... What I sensed in you is...
 * Aqua....Ven....someday, I will end this.
 * Xe....ha.....nort..... Where are you?

Trivia

 * At the end of Birth by Sleep, the Lingering Sentiment doesn't wear a cape, but when Sora faces him ten years later, he does. This change was made so that Kingdom Hearts Birth by Sleep would play faster.
 * Certain changes are noticble between The Lingering Sentiment in his Final Mix self and Birth by Sleep self such as its keyblade being bigger and armor being darker. This is thought to be because of his stance in the Keyblade Graveyard.
 * The Lingering Sentiment is the second superboss to gain a playable role, succeeding Xemnas.

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