as the name describes, these universes have been devoid of life enterally, often though a brutal conflict of some kind, often described as a "Cold place with no light in it", despite this (or because of it) these universes have became the sites of many operations, ranging from Prisons and Weapons testing to more illegal operations from groups that otherwise want to remain unknown
the name used to describe the 875 universes that had a majority of its population of Pure Combines/Kilominitics, and what made up of the "Homeworlds" of the Empire of the Combine Race during its reign. After the First war, it became an unstable region with many Combine Remnant groups being active and heavily supported by the population, but, by the time of the formation of the Multiversial Federation, it have become a stable region once more.
the name used to describe the 595 universes that was controlled by the Second Human Empire and the Third Human Republic/ United Federation of Species, these universes are the remains of the Human, Forerunner and Prothean Interuniversial Empires, however the ottsels are not included namely because of the fact that their Interuniversial Empire is still alive and active (albeit weaken severally and shattered in more ways than one)
also known as "The Ruins" and "The Shattered" is the name used to refer to all the other universes that do not fall under the previously mentioned universe classification, these universes are called this because of the fact that these universes and their civilizations are living (metaphorically) in the ruins of the Ancients