Atrium Carceri - Faces of War

'Phrenitis' takes the listener to a twisted place where the walls between worlds are razed. The ruinous cities of wars long past, where time itself is but a prisoner and the warlords roaming their purgatorial halls are free to destroy the very foundations of the natural order. (Cold Meat Industry)

Ambient music is a musical genre in which sound is more important than notes. It is generally identifiable as being broadly atmospheric and environmental in nature. It's primary feature is that the music is intended to drift in and out of the listener's awareness while creating its effect on the listener's consciousness.
Dark ambient is a general term for any kind of ambient music with a "dark" or dissonant feel, but often involves extensive use of digital reverb to create vast sonic spaces for frightening, bottom-heavy sounds such as deep drones, gloomy male chorus, echoing thunder, and distant artillery. It has an eerie feel. Generally the music tends to evoke a feeling of solitude, melancholy, confinement, and isolation. However, while the theme in the music tends to be "dark" in nature, some artists create more organic soundscapes. (Wikipedia)

What you hear:
("Atrium Carceri" - "Faces of War" from the album "Phrenitis")