Lingering Will

The Lingering Sentiment (留まりし思念) is an unlockable secret boss featured in Kingdom Hearts II Final Mix and briefly playable character at the climax of Kingdom Hearts: Birth by Sleep. It is merely the lost soul of Keyblade wielder Terra residing within the man's discarded armor, the soul and armor lost to him during the final battle with Master Xehanort.

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.

Kingdom Hearts Birth by Sleep
After losing his first battle with Terra, Master Xehanort witnessed the creation of the X-Blade along with the young Keyblade wielder. Seeking to use the man's darkness as a younger, more powerful weapon as he ventured further into the mysteries of the Keyblade War, Master Xehanort then proceeded to unlock his heart. Terra attempted to shield himself with his armor, this proving to no avail, the man becoming a younger incarnation of Master Xehanort. Just as the new Xehanort began venture away from the place of Terra's fall, he soon found himself trapped within a force field, turning to find Terra's armor standing reassembled before him, Terra's soul having found residence within it. Angered by Terra's defiance, he then engaged the Lingering Sentiment in a long, fierce battle.

In the end, the Lingering Sentiment emerged victorious, knocking Xehanort unconscious. The armored figure then thrust its Keyblade into the ground, kneeling down (in a similar fashion to that of its Kingdom Hearts II Final Mix incarnation upon its meeting with Sora eleven years later). Soon after, Xehanort consumed in an immense sphere of light, the result of Aqua and Ventus shattering the X-Blade during the process of defeating Vanitas. Kingdom Hearts then disappeared from the sky above, the Lingering Sentiment to remain alone in the Keyblade Graveyard, promising to Aqua and Ven that someday, somehow, it would put an end to the conflict.

Kingdom Hearts II Final Mix
After the defeat of Xemnas, a portal to the Keyblade Graveyard appeared in Disney Castle. Sora, Donald, and Goofy proceeded to enter the portal and find the Lingering Sentiment, which at first mentioned Aqua and Ventus. It then mistook Sora as "the one he has chosen," wondering if Sora was Xehanort before finally attacking him. Sora managed to defeat the Lingering Sentiment after an intense battle, and the Lingering Sentiment respectfully acknowledging Sora as a true Keyblade master. If Sora returned for another match, the Sentiment would accept its defeat, but not before stating that it had nothing left to give him and that all it had left is its hatred for Xehanort.

In the game, the Sentiment speaks to Sora through enigmatic sounds, much like Xemnas did 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.

Fighting Style
When playing as the Lingering Sentiment during the final battle with Xehanort at the Keyblade Graveyard in Kingdom Hearts Birth by Sleep, it should be noted that it loses Terra's ability to use D-Links and Command Styles. Retaining Terra's immense power, the Lingering Sentiment only has access to the basic abilities equipped before the battle begins. It is also able to use magic to some degree.

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..."
 * "Xe....ha.....nort..... Where are you?"

Trivia

 * Upon its creation at the end of Kingdom Hearts Birth by Sleep, the Lingering Sentiment doesn't wear a cape, but when Sora faces it ten years later, it does. This change was made to avoid lagging issues in Kingdom Hearts Birth by Sleep.
 * Certain changes are noticeable between The Lingering Sentiment in its Kingdom Hearts II Final Mix and Kingdom Hearts Birth by Sleep incarnations, such as its Keyblade being bigger and armor being darker.
 * The Lingering Sentiment is the second superboss to gain a playable role, succeeding Xemnas.
 * The Sentiment's first quote, about Sora not being "the one he chose" refers to when Terra met Riku on Destiny Islands as a child and saw him to be his successor.

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