Mementos

Mementos is the Palace for everyone's hearts. Free missions unrelated to the story are done here so that they can steal the hearts of humans on these missions. The Phantom Thieves of Hearts explore the dungeon by using Morgana's bus form. While it is initially an optional place meant for grinding levels and solving optional missions, it later becomes the final dungeon when Yaldabaoth awakens his true form, the Holy Grail, within it. It appears to be a massive series of subway tunnels with wooden train tracks in place of rails, with various features of a prison such as chains or bars. Where a Shadow Self inhabits the area, the walls develop red cracks that resemble a spider web or fractal patterns, and the veins that power Yaldabaoth's regeneration become prominent. Mementos is divided into multiple "paths", each of which has its own unique architecture and floors, referred as "areas". They are randomly generated and areas open up as the fame of the Phantom Thieves grows with each Palace they defeat.