Mementos is a tri-platform stage with a slanted main stage, similar to that seen in Meta Crystal in the original Super Smash Bros. on the Nintendo 64. Every once in a while, a wall will spawn on either side of the stage or from the stage's ceiling, and a train will appear near the bottom of the stage, which can damage players if they touch it. At any given time, the trains and the wall will not appear simultaneously.
The stage's main design, based on Persona 5, uses a red color scheme with star designs and black-and-white halftone motifs. If a song from Persona 4 or Persona 3 is playing, the color scheme will change accordingly to yellow or blue respectively. The platforms change design to incorporate flowers and checkerboard patterns (for Persona 4) or clocks and triangular patterns (for Persona 3). Similarly, the backdrop changes to include rainbow-like streaks (for Persona 4) or a moon (for Persona 3). If Joker wins a match on Mementos with these alternate designs, his victory screen and subsequent music will change accordingly.
The Morganamobile occasionally appears in the background, dropping off some of the other Phantom Thieves of Hearts.
Mementos is a location that is visited several times throughout Persona 5. Part of the mysterious Metaverse, it is the Palace of the collective unconscious. Located under the subway tunnels of Shibuya, it is lined with train tracks and train platforms that Shadows, the game's enemies, actually use to traverse the dungeon.
The Phantom Thieves are able to visit Mementos in order to take requests to change the hearts of people whose distortions are not bad enough to cause their own individual Palace to manifest. Exploring Mementos' randomly generated floors also offers the opportunity to gain money and EXP, as well as capture Personas that the player may have missed in a previous Palace. An entrance to the Velvet Room is conveniently located at the entrance to Mementos, allowing a player to summon or fuse new Personas.
As the Phantom Thieves' notoriety increases, they are able to explore more and more of Mementos. Mementos serves as the final dungeon of the game, as the team sets out to change the heart of society at large. They manage to reach the deepest depths of Mementos where they find the Holy Grail, an incarnation of Yaldabaoth, the God of Control. Yaldabaoth easily defeats the Phantom Thieves and merges Mementos with reality before being defeated by the Phantom Thieves for good.