- Background Music: Gentle Madman (Research Lab), Out of Kindness (Outdoors), I Believe (After sending calling card)
- Available: October 3rd (First glimpse), January 3rd (First exploration), January 9 (Saving Sumire), January 10 (Start of exploration)
- Deadline: January 9 (Snapping out teammates from the dream world), February 3rd (Final)
- Owner: Takuto Maruki
- Location: Oodaiba Stadium construction site
- Keyword: N/A
A world within the Metaverse that is seemingly created by Takuto Maruki, although unlike the others, it is easily detectable in the real world even by non-Persona users and Takuto is physically present as opposed to other palaces. It appears as a large, towering structure of glass and gold, with the interior resembling a mental health center.
It first emerged on top of the Oodaiba construction site after Kunikazu Okumura's death, which is a stadium that is about to be reconstructed into a cognitive research center. Kasumi Yoshizawa requests the protagonist to come there and investigate after a threat to revoke her scholarship is issued. Once the duo enter, its interior resembles a research lab with cognitive copies of patients looking for happiness. When the protagonist and Kasumi enters the research hall, an image of Kasumi's supposedly dead sister appears and mutters "I...instead...my..sister," implying Kasumi was the one that died, causing an adverse reaction to her. The image was quickly squashed by a shadow which bursts out into a Biyarky to attack the party, in which Kasumi awakens her Persona Cendrillon and fights it alongside the protagonist. Kasumi can now defend herself inside the Metaverse, although she does not officially join the party.
During January 2, Kasumi can detect the Palace again and requests the protagonist and Akechi to investigate. The trio explore it and as they go further, more of the truth behind Kasumi is revealed, and this causes an adverse reaction to Kasumi, as she sees her sister had a beauty mark and brown hair. This resulted in Kasumi's disguise breaking off part by part, eventually causing her to attack enemies mercilessly in distress.
As the trio explore further, they finally encounter the owner of the Palace; The former school counselor of Shujin Academy Takuto Maruki, who is reduced into half a madman with only a shadow of his former self, although he appears to be self-aware that he is doing wrong. He claims that reality is too painful and he used his magic to help them escape reality, and he only wanted to bring forth happiness to humanity, ignorant to the fact that he can cause stagnation and make himself not very different from Yaldabaoth. Once he is unable to talk past the protagonist and Akechi, he displays the truth of Kasumi Yoshizawa; The "Kasumi" whom the protagonist encounters is in fact, a fake called Sumire Yoshizawa who was always jealous of her sister, the real Kasumi's talent which degenerated into suicidal depression, eventually resulting in a suicide attempt by throwing herself onto traffic a month prior to the protagonist's arrival to Cafe Leblanc that causes Kasumi's very own sacrifice by taking her place. Kasumi now completely breaks off and reveals herself to be actually the extremely vulnerable Sumire in disguise. Takuto then confiscates Sumire for his own use then sends out a Hastur to attack the party. He then grants them a 9-day window to snap out all other party members from his magic.
If the protagonist and Akechi return to him on the next day, he will offer the protagonist to accept his reality. Doing so will result in a bad ending. If he refuses, he will awaken Kasumi and use her natural denial of the truth to provoke her into attacking the party; Akechi leaves the protagonist alone to deal with her in fears of he will kill her because of his combat instincts. Kasumi will go down easily after a few attacks. Once this is done for, Takuto will then summon a series of electric cables to force Cendrillon to go berserk and attack the protagonist and Akechi all the while summoning Biyarky for it to absorb. The duo is no match for Cendrillon's berserk state and was left helpless until Ryuji Sakamoto block the final shot and the rest of the Phantom Thieves of Hearts joins them. They gather to defeat the berserk Cendrillon and Takuto restores Sumire into Kasumi just to give them a fighting chance. He then tells them to meet him after 30 days so they can change his heart.
Should the party miss this deadline, Takuto will summon the protagonist into his office at Shujin Academy in his dreams, with the protagonist wearing his Velvet Room prison uniform. Takuto tells him to sleep for an eternity, with the scene cutting to the protagonist lying in bed in LeBlanc with his phone long dead, and his room covered in dust and cobwebs. He is unwilling to leave is bed as he is unable to think of anything, and not even Lavenza is able to reach out to him as the butterfly vanishes as soon as it tries to.
The Palace is the largest one in the entire game and exploring it requires at least two days alongside an exploration to a new area in Mementos to its true bottom in order to prevent the palace from channeling its power, making it a total of three days. The lower levels are consisted of a lobby, a control center, a laboratory, a warehouse and finally a mental health check center, and its cognitions are patients that slowly degrade into shadows of their former selves that only want blind happiness. Since Takuto does not see anyone in a distorted manner, these cognitions appear as human and passive. Its Shadows resemble black, vaguely humanoid beings that are either undressed or in therapist clothing, while guard captains have large, exaggerated muscles.
The mental health check center has no enemies on its own, although the party is presented with a quiz which trials its patients for how much they know about Takuto's very own version of true happiness. There are 2, 3 and 5 answers respectively, and any answer that does not correspond to Takuto's current ideals will result in the party being attacked by a normal Shadow encounter. At the second and third quizzes, they can also cheat by looking inside the windows of the control room for shadow therapists.
The upper floors resembles a paradise with patient cognitions doing nothing but laughing wildly and sending themselves to air; This area features a color puzzle that requires the party to match the lights of the controllers into the gate's corresponding colors to open various areas, including creating bridges or opening gates blocked by vines. A cheatsheet can be seen near the controllers to assist the player.
Several areas in the Palace are barricaded by a quiz about Takuto's mindset; All of these correspond to a cassette tape that must be viewed, which reveals parts of Takuto's past. It turns out that in the past Takuto's ex-girlfriend, Rumi got her entire family murdered and fell into catanonic depression as a result, and the word "family" became her trigger word. In a desperate attempt a being of infinite wisdom contracted him and gave him magical powers to cope with severe mental conditions, and Rumi was mysteriously recovered from her depression. However, she also lost all of her memories and thus Takuto distanced from her.
He then became an accomplished cognitive psience researcher in the lines of Wakaba Isshiki, although his statments are often rejected for being purely original research. He also found that the powers are in fact, dangerous, and he will not use it to cure depression unless when he has no other option. He opened a clinic afterwards and met Sumire Yoshizawa who was so depressed that she refused any traditional methods that he used and actively asked him to turn her into Kasumi, which he did; Sumire was transformed into Kasumi and was seemingly cured of her depression and survivor's guilt.
During the day of reckoning on the 23rd of December, it was found out that Masayoshi Shido had stole his research for nefarious purposes, which angered him greatly. Yaldabaoth enacts his final plan for world domination and accidentally causes the being of wisdom to be transformed into a tentacled monster. He was driven insane and enacts his plan for mass salvation after Yaldabaoth's fall.
The treasure chamber reveals itself to be the Garden of Eden, where barely dressed cognitive patients enjoy their life there and become ignorant to their surroundings. Once returning to the real world, the protagonist actively meets and sends him a calling card in LeBlanc on the 2nd of February, which seemingly does not cause any psychological distress on him unlike other targets, implying that he is fully prepared for it.
During the next day, the final confrontation begins and the party and Takuto fight inside the central dome of the Garden of Eden, in which he changes his outfit into a golden priest garb and summons his Persona, Azathoth. The party must defeat either Azathoth or Takuto twice, with one tentacle preventing Azathoth from being damaged, one healing Takuto and other casting buffs or debuffs; All of these tentacles appear to swap weaknesses once Takuto regenerates them. After defeating Azathoth, The Palaces collapses and reveals its treasure, a fire torch. Takuto however, quickly confiscates the torch and fuses it into Azathoth, restoring into its true form, the Being of Infinite Wisdom, Adam Kadmon. This implies that Yaldabaoth accidentally separated the torch from Adam Kadmon and caused it to degenerate into the blind Azathoth, and thus Takuto began misusing his magical powers to blind others from the truth. After being defeated once, Takuto fuses himself into Adam Kadmon and is basically invincible; Only by the protagonist's party members stalling its fist while Futaba scanning its head to be fully vulnerable while distracted can he deal a final shot to its head and destroy it completely.
As Adam Kadmon is destroyed and the Palace collapses, Morgana transforms into a helicopter to rescue the rest of the thieves; However, Takuto now pulls the protagonist into the ground and challenges him to a fist fight. After a while both collapse into the floor and Takuto attempts to commit suicide by falling off the Palace's remains, only for the protagonist to save him, all the while when Morgana rescues both to leave Oodaiba. It should also be noted that both ways that the protagonist can respond to Takuto have the same meaning and thus will prevent him from falling to his death.
After the Palace collapses and Adam Kadmon destroyed, Takuto lost all of his magic, resulting in everything returning to normal; the protagonist is now in juvenile hall where all of his confidants, including ones that he maxed at the third semester support him in leaving it, Sumire lost all of her powers, Akechi is once again found missing, and the treasure that is Adam Kadmon's torch reveals itself to be the newsletter about the murder of Rumi's family. The protagonist keeps this newsletter as a memento.
- This palace has the longest clear deadline in the entire game, at 30 days.
- This Palace bears similarities with the musical dungeon of Persona Q2, as they are heavily associated with toxic escapism and false happiness, are the largest dungeons in their respective games, and contain recordings of how their hosts became distorted.
- After sending the calling card to Takuto, the in-game map for this palace becomes a BGM visuzalizer.