Brain

Brain is a Keyblade wielder who appears in Kingdom Hearts Union χ. He is a member of the Dandelions and was chosen by the Master of Masters to lead a Union after the Keyblade War. Like the other new Union leaders, he was given a book with laws set by Master Ava.

Before Kingdom Hearts Union χ[Cross]
Brain is chosen by the Keyblade and awakens within Daybreak Town, where he joins a Union of fellow Keyblade wielders. Eventually, he is approached by Ava and informed of the coming end of the world, subsequently joining the Dandelions. He receives training in preparation for crossing Worldlines in order to avoid taking part in the Keyblade War, thus ensuring the survival of light.

Brain meets with Ava on the hill overlooking Daybreak Town, where she asks him to become a Union leader. Though Brain initially believes that he's not cut out to be a leader, he changes his mind after hearing that the Master of Masters was the one to choose the Union leaders. Brain becomes suspicious when Ava informs him that she can't reveal the other four leaders just yet, and so Ava asks him what would happen if the world's fate was already decided. Extrapolating, Ava points to the Book of Prophecies, asking what would happen if you could change what was written within it, with Brain wondering if the Book would change as well. Ava explains that there's no way of knowing, which means there would be a future that was not planned out. Thus, Ava provides Brain a copy of the Book of Prophecies, going against the predetermined future, as he'd not been chosen by the Master of Masters to receive it. Ava then places the memo from the Master of Masters in Brain's copy of the Book of Prophecies, intending for him to read it when the time came to decide their futures, hoping that her message to Brain would be clear at that time.

Kingdom Hearts Union χ[Cross]
As per Ava's instructions, the new Union leaders are to come together in the Keyblade Graveyard following the Keyblade War. Brain is the fourth to arrive, after Ephemer, Skuld, and Ventus. Brain questions if the rules set forth by Ava are absolute, expressing his wariness to trust Ava because she wants them to lie to the Dandelions about the Keyblade War. Thinking of how had suffered, Ephemer states that no one else should have to carry the burden of the past, a sentiment Skuld and the others accept.

After the final Union leader, Lauriam, arrives, the Union leaders go to Daybreak Town and enter the Foretellers' Chamber, where Brain finds a copy of the Book of Prophecies and starts flipping through it. When Skuld proposes that they begin choosing which Union each of them will lead, Ephemer recommends that they maintain the Union χ in order to prevent the conflicts of the past world, with the other Union leaders agreeing to reconstitute the old system later as stated in the rules. Brain then suggests that, while the Dandelions are reliving the events of the past, they collect the necessary ingredients to create new Spirits and sends Ephemer, Skuld, and Ventus to collect the ingredients while he and Lauriam stay behind to make the necessary preparations.

Ephemer calls a meeting in order to discuss the Shift Pride, but when Lauriam doesn't make an appearance, Brain informs the group that Lauriam was attending to a personal matter and had informed him that, whatever the circumstances may be, he'd side with Ephemer. Continuing, Ephemer mentions that the Rule Book states that they are meant to impose the Shift Pride, which Brain notes is essentially like a friendly contest between wielders, which he is decidedly in favor of. Meanwhile, Ventus and Skuld oppose the Shift Pride, not wanting wielders to raise their Keyblades against one another again. Ephemer finalizes the Shift Pride by voting in favor of it, explaining that he'd been inspired by a conversation with Lauriam to utilize the data of the Keyblade wielders which exists in the data versions of the worlds they visit ever since the Keyblade War. Given his conversation with Lauriam, Ephemer also mentions that Lauriam had been searching for someone who should have become a Dandelion, but he has yet to see them, being the reason why he'd sought to search the data for this person. With this in mind, Brain suggests that they don't pry, as it seemed like something Lauriam wants to pursue on his own.

When Lauriam returns, he asks Skuld about his sister, Strelitzia, revealing that he had been out looking for her. Lauriam explains the circumstances of Strelitzia's disappearance, including the fact that she had been pursuing an individual in order to convince them to join the Dandelions. Brain chimes in to point out how odd it is that Strelitzia, who was hesitant to become a Dandelion herself, would be so desperate to convince someone else to join.

After Ephemer and Lauriam leave to investigate Strelitzia's disappearance, Ventus asks Brain about the book that he's reading. Brain explains that even if they overwrite the Keyblade War, the world is still on a destructive path, and resolves to be the virus that overwrites that destiny.

Making his way to the Control Room, Brain encounters glitches and gets to work attempting to stop them. Ephemer, Ventus, and Player, whom Ephemer introduces, manage to catch up with him and question what's happening concerning the glitches outside. Brain reveals that he's managed to stop an infestation for now, before going on to explain how, in the world before the Keyblade War, they were able to visit worlds of the future via the Book of Prophecies. As these worlds currently existed, they did not require the Book of Prophecies to reach them, because they were all connected to Daybreak Town, though it would have been hard to reach them due to the scope of the world. However, since the Keyblade War, these worlds have become disconnected. Having been foretold, the worlds were recreated as data in order to ensure that they and their respective futures could still be accessed virtually, through the data Daybreak Town. When Brain poses the question of whether they are in the real or the data Daybreak Town, he notes that the presence of the glitches suggests that they are within the data version.

Reminding Ephemer that he'd mentioned Daybreak Town acted as a portal to the futures of worlds that already existed, Brain explains that they've since connected to a world that doesn't yet exist in their world or time. When this world connected to theirs, the glitches started to appear, and though it was impossible for Brain to completely sever the connection, he has since managed to stabilize it, though they would have to investigate in order to fully understand what's going on. To this end, Ephemer volunteers, though Brains suggests their leader stay in case something goes wrong. Instead, Brain suggests that they send a Dandelion, and Player is quick to volunteer, despite the danger - though Ephemer remains resolute in going with Player. Admitting that it couldn't hurt, Brain agrees and opens a path to this new world for Player and Ephemer.

Ephemer soon returns alone, trusting Player to continue exploring the new world without him. When Skuld and Lauriam arrive in the Control Room, Ephemer and Brain explain the situation and add that they'd pursued Darklings into this new world, and soon after, enemies from their world began appearing in this new world, suggesting that the Darklings were responsible. Ventus mentions that they've also seen Noise of Ava's meeting with the Master of Master, while Lauriam mentions having seen Noise of Strelitzia as well. With all of the evidence presented, Brain concludes that they must be in the data Daybreak Town, causing Ephemer to ask whether or not there even was a real Daybreak Town, while Ventus wonders if it had been destroyed. Brain asserts that there is no way of knowing, as they have been completely cut off from their original world, and suggests that there must be someone behind all this. He reaffirms his vow to be the virus that overwrites the world's destruction.

Brain looks to the Book of Prophecies for answers, and is approached by Lauriam, who explains that he'd spoken with Elrena again. Lauriam recalls how Brain had pointed out that it seemed odd that Strelitzia had wanted someone to join the Dandelions when she herself had been hesitant, and reasons that something must have happened that made her certain that the Keyblade War would occur. Brain asks for time to think, and when Lauriam leaves, Brain reads the memo Ava had left for him in the Book of Prophecies.

Afterwards, Brain summons his Chirithy and has him collect Ventus and Skuld for him, whilst he meets Ephemer on the hill overlooking Daybreak Town. Brain tells Ephemer that only one of the five new Union leaders was supposed to have the Book of Prophecies, but he hasn't had to use the Book of Prophecies until now, as all the worlds were replicated in data as insurance. After having read Ava's memo, Brain realized that it wasn't meant to be him. Furthermore, Strelitzia was meant to be one of the new Union leaders. Despite Ava having been the one who had changed who received the Book of Prophecies, Brain expresses that he doesn't believe it was her intention to change the new Union leaders. Chirithy, Ventus, and Skuld then arrive, and he asks them where Ava had told them she intended them to become Union leaders. Ventus reveals she'd done so near the clock tower, rather than on that very hill as she did for the others. Brain then reveals that Ventus was never supposed to be one of the new Union leaders.

Brain asks Ventus about what he remembers, to which Ventus recalls meeting with Master Ava in an abandoned house. Brain questions whether the person Ventus met was really Master Ava, believing that it may have in fact been Darkness, and suggests that everyone return to the tower.

After Ventus is put in his room to rest, Brain consults with Ephemer and Skuld. He concludes from Ventus's description that he was there when Strelitzia disappeared, but affirms along with Ephemer that Darkness must be the true culprit. Brain believes now that Darkness is inside Ventus and that it remains close. He suspects it will come after them as it did Strelitzia. Brain, Ephemer and Skuld are then approached by an injured Lauriam, demanding answers about happened to his sister. As Skuld and Ephemer try to calm Lauriam down, Ventus enters the room and admits he is responsible for what happened to Strelitzia. Brain tries to stop Lauriam from attacking Ventus. In the midst of the conflict, Ventus collapses on the ground and Darkness emerges from him.

The Union leaders discover that Darkness was responsible for replacing Strelitzia with Ventus. Brain questions Darkness about its motive, its relationship with the Master of Masters, and why it chose to show itself now. Finally, he asks if Darkness is alone, to which it answers that it is. Brain then summons his Keyblade and battles Darkness alongside Ephemer and Skuld. The three of them are defeated, and Darkness tells them that the world is fated for destruction. Brain retorts that regardless of what is fated for them, they believe in Ephemer, their leader. Ventus then awakens and clashes with Darkness, ending the battle.

As the data world begins to deteriorate, Brain and the others make plans to escape back to the real world using the lifeboats. Brain gives Ephemer his Keyblade, Master's Defender, and the Book of Prophecies before returning to the real world alongside Lauriam, Ventus, and Elrena. Back in the real Daybreak Town, Brain sends Lauriam, Ventus, and Elrena away from the collapsing world in the lifeboats. Brain is then approached by Luxu, who asks what his plan is. Brain asserts that he will stay in the collapsing Daybreak Town for as long as it takes to figure out how to save all the Dandelions. Luxu compliments Brain's intelligence and comments that it's a shame Brain only has one lifetime to live. At some point after this exchange, Brain returns two of the lifeboats to the data world for Ephemer and Skuld.

Sometime after the destruction of Daybreak Town, Luxu with Brain's appearance is seen walking through the Keyblade Graveyard with the Black Box and the No Name Keyblade.

At an unknown point in time, Brain wakes up in a city. He is approached by a hooded figure who introduces himself as Sigurd and tells Brain that his arrival on this day had been foretold. Brain begins to follow Sigurd, but is distracted as they walk past a large fountain with a statue. Sigurd explains that the statue is of Master Ephemer, the founder of the town, which he reveals to be Scala ad Caelum. Brain replies that he knows, and that Ephemer was a good friend.

Design
Brain has gray eyes and black spiky hair, which droops down over his eye. He wears a black coat with rolled up sleeves, gold buttons, and a large collar, grey pants, black cowboy boots, and silver cross-shaped earrings. His face is initially concealed by a black fedora that sports a black feather with a tan streak down the middle.

Personality
Brain is cool, calm and mysterious. As noted by Ava and Skuld, Brain is clever, as shown as during the mystery of Strelitzia's death, having deduce Ava's intentions was to only change who received the Book of Prophecies, not the leaders who were chosen, and Ava would have wanted to make sure that Strelitzia was safe.

Like Ephemer, Brain was hesitant about becoming a Union leader, believing he was not capable of fulfilling the role, but resolves to perform his duties and prevent another Keyblade War from occurring.

Abilities
Brain wields the Master's Defender Keyblade.