Pluto Castle (プルート城) is a dungeon found in Shin Megami Tensei IV.
A spiked, dome-shaped fortress found southeast of Kasumigaseki across a broken bridge in the world of Blasted Tokyo. It is named after Pluto who resides there. Its halls are filled with Pluto Soldiers and demons who are on the orders of the Gods to annihilate mankind. The entrance was guarded by a Cyber Horde of Pluto Soldiers. The dungeon is made of hallways that lead to circular rooms, and the place appears organic in nature, with lights shining from the ground. Yellow spots found in certain rooms take one up to the next floor, but jumping down through holes is required to get down to the bottom floor as the spots only go up.
A group of Pluto Warriors is found on the third floor, blocking the way further in. The fourth floor has Cyber Hordes start appearing as common encounters. Pluto Giants block a path on the first floor that leads to a different part of the third floor. Pluto himself resides on the basement floor, from where he spews his poison to the atmosphere.
Flynn may receive the Challenge Quest Yomotsu Okami's Revenge post-alignment lock in the Chaos and Neutral paths. Izanami has been struck with the curse afflicting the various underworld gods and seeks to resume Pluto's mission. She is fought at the same room where Pluto was defeated at the Castle.
Later on, in the "Ancient One of the Sun" DLC, the Ancient of Days will attack the remnants of human civilization at Tokyo, forcing the remaining survivors to hole up at Pluto Castle.