Location from Persona 5 Royal by Atlus
The deepest stratum of Mementos, where the Holy Grail — Yaldabaoth — resides. The Prison of Regression: the place humanity built for itself by choosing comfortable slavery over difficult freedom.
The Depths of Mementos is the psychological bottom of humanity's collective unconscious — the level reached only when enough people have surrendered their will. It is not guarded because it does not need to be; people walked here willingly. Yaldabaoth's plan required the public to choose to stop thinking for themselves, and they did. The Prison of Regression is the architecture of that choice. The Phantom Thieves descend here only after defeating all seven Palaces — and they find the entrance locked, impassable, because the public voted to stay. The November plot beat is the Phantom Thieves' dissolution and Joker's capture — events the depths already anticipated.
The subway architecture collapses here into something older and stranger — stone pillars, vaulted ceilings, tracks that bend upward. The walls carry images: crowds, cities, ordinary people going about lives of willful ignorance. A massive door seals the way to the throne. Behind it, the Holy Grail pulses gold in a void.
Also known as: Depths of Mementos, Prison of Regression, Qliphoth World Gateway, Mementos Bottom