Autocosm: a plural network of selves, each existing in their own dimension/reality/universe, all of which share a soul and/or a sense of "self"-ness with one another. There is a central self, called a metasoul or metaself, from which all other selves, called lunen, are derived from in some way.
Extended definiton/extra notes:
The metasoul exists in a realm called the soulscape, which functions similarly to a headspace or paracosm, in that it can vary in size, structure, visibility, stability, etc. It can also have different areas or be split into multiple connected realms.
The metasoul's consciousness extends to all lunen, and they are able to sense, feel, and remember everything their lunen do. Metasouls do not do anything equivalent to "fronting" but their presence in the lunan's consciousness, and the lunan's awareness of their presence, can vary. They may or may not be able to communicate outside of the soulscape. Not all lunen know they are a part of an autocosm, but the metasoul is aware of all lunen.
Lunen may or may not be aware of one another and cannot communicate directly. However, there is an inherent connection between all lunen that drives them to become aware of one another, and possibly experience parts of one another's lives in a manner akin to memories. Lunen may be able to communicate with each other in the soulscape, via the metasoul relaying messages, or not at all.
The soulscape can be accessed by lunen through various methods, such as meditation, reality shifting, dreaming, or other altered states of consciousness. The metasoul may also "summon" a lunan to the soulscape, and some lunen may be able to access it without effort or be connected to it at all times.
Beings other than the metasoul may inhabit the soulscape. These are called habitans. Habitans can be of any appearance, personality, or level of sapience. The origins of habitans vary; they can be created by the metasoul, spontaneously form in the soulscape, or originate from somewhere else. Habitans may or may not be considered part of the autocosm. They are not a part of the "self" the autocosm is based on, but they do inhabit it nonetheless. Not all soulscapes have habitans.
Autocosms may have different origins, although a spiritual aspect is inherent due to the concept of souls being integral. This spiritual aspect need not be focused on or considered important to the identity, though, and other aspects (such as psychological) can be present. Lunen also have different origins; they may be created willfully by the metasoul, be split off from them, spontaneously emanate, etc. (Do not use -genic terms unless you also identify as a system, I coined -genesis as an alternative term grouping for non-system alterhuman origins, you can coin those as you see fit).
As the concept mirrors aspects of many other alterhuman and plural identities, it is possible for autocosms to identify with those as well. Autocosms can be systems, lunen can be godshards/othershards, metasouls can be archetropes, soulscapes can be hearthomes, habitans can be thoughtforms, etc. The only identities autocosms incorporate inherently are plural and alterhuman. However, as they are variations of one self, it is common for lunen and metasouls to be kin with one another.
Oh my stars, this is the most complex term I've ever coined. I'm so happy to finally be able to express my alterhuman identity in a more specific way though, so it was well worth the time and effort! If you have any questions, feel free to ask me, and feel free to message me if you think you might be part of an autocosm. I know that it's a lot lol and I can do an FAQ later if needed. Feel free to repost on pluralpedia, termora or other applicable wikis, just don't change the definition (you can include parts of the extra notes on the wiki page however you want as long as it isn't inaccurate though). I'll be posting flags/defs for lunan, metasoul and habitan soon :3
(Also, I need help with an image description again due to my insistence on a weird flag. Sorry about that, I just don't know how to write descriptions for complex flags in an accessible manner).