Empyrean is a location in Persona 3 FES. It is the seventh door in the Abyss of Time. For the first 9 floors, Empyrean resembles a fancy and elegant building, with a light palette of colors. The next 10 floors have blue walls and metallic floors, and the last 7 floors have the same design that the first ones. At the 27th floor, there is a door into Aigis' past.
Empyrean, properly Empyrean Heaven, is the place in the highest heaven, which in ancient cosmologies was supposed to be occupied by the element of fire (or aether in Aristotle's natural philosophy).
The Empyrean was thus used as a name for the firmament, and in Christian literature, notably the Divine Comedy, for the dwelling-place of God, the blessed, celestial beings so divine they are made of pure light, and the source of light and creation.
On the 25th floor, there will be two Rare Chests that contain the Ultimate Weapons for each character.