The Deep Mania seems to be an extradimensional space that links the consciousnesses of all living things affected by Mania and is the origin for all spiritual energy. Currents and movements within the Deep Mania have a symbiotic, push-and-pull relationship with people and events in the real world. The Deep Mania is profoundly influenced by the collective will of humans, and human consciousness both shapes and is shaped by the forces that are native to that plane. Through resonance, these interactions can also have consequences that reach much farther metaphysically than can be explained with physical cause-and-effect. The most dramatic example of this is the appearance of Black Rings in DisCity causing natural disasters on the other side of the world in Eastia.
While normally inaccessible except by extraordinary means, an individual's consciousness can create a kind of pseudo three-dimensional space within the Deep Mania where the mind can affect the fabric of the imagined reality. These metaphysical spaces come in many forms and go by many names, including dreams, mirages, spiritual realms, and illusory worlds. Visions of the Deep Mania frequently involve the imagery of a field of red or blue crystal flowers. Many of the most powerful and mysterious forces in the world of Path to Nowhere work by accessing the Deep Mania. At the center of the Deep Mania is the mysterious Source.
The Deep Mania is also home to otherworldly lifeforms, many of which have crossed over into the physical world since the dimensions became linked after Nightfall. Notable examples are Apostles, Great Existences, and the Nightmare clan. In the in-game enemy profiles, the category of enemies called "Native Species" includes many Mania-based monsters and creatures created by thoughts or fantasies, possibly indicating that these are all beings that originate from the Deep Mania as well.
In addition to the innumerable number of temporary spiritual realms, there are a number of other metaphysical spaces which seem to be stable, permanent locations in Deep Mania. These include:
- Black Rings: All Black Rings are semipermanent realms that exist as gateways between physical reality and the Deep Mania. They continue to exist for as long as their Corpus lives, and are shaped by the will and desires of the individuals whose Mania allowed the Corpus to ascend. They are the only known way by which a spiritual realm can be created in a real, physical space.
- Hamel's illusory world: Within the spiritual realm of BR-001, Hamel created an additional spiritual realm in which the DisCity Carnival continued to appear lively and joyful. The soothing nature of this realm pacified the thousands of Corruptors inside the Black Ring and prevented the ring's Corpus from maturing to its final form.
- Nightmare Space: The Nightmare Space is an illusory realm created by the consciousnesses of those who participated in the Keylan expedition. It is occasionally accessed in the dreams of Sinners who have seen the Phantom Moon. Activity in this space leads to immense pressure on the human mind and eventually depletion of sanity. The Nightmare Space has also been known to overlap with the interior of BR-000, such as on N.F. 113.04.20 when Dreya appeared in DisSea.
- The Observatorium: Unlike other spiritual realms, the Observatorium was intentionally created by Paradeisos and represents the outermost boundary where human reason can venture into Mania. It is a structured domain under strict jurisdiction of the Rules and is the key to Paradeisos's Hush system. By establishing an anchor of reason within the Deep Mania, the Observatorium allows the Hush a safe space from which to monitor the currents of Mania. It is also unique among spiritual realms in that the Hush’s consciousness is able to freely access or awaken from it at will.