Cosmic Entities

THE FOLLOWING CONCERNS A SPECIES CLASSIFICATION THAT IS PURELY OR PREDOMINANTLY FANONICAL.

Canon

The Sonic series (in games post Dreamcast at least)¹ has featured multiple characters that exhibit an metaphysical, superdimensional, or otherwise goldike traits in their abilities, biology, and/or behaviours.
Noteable examples include:

• Illumina from Sonic Shuffle;
• Solaris from Sonic the Hedgehog (2006);
• Argus fromSonic Chronicles: The Dark Brotherhood;
• Dark and Light Gaia from Sonic Unleashed; and
• The End from Sonic Frontiers.

Fanon

The above entities are all superdimensional lifeforms known as cosmics. I have left out some powerful characters (Black Doom, Mother Wisp) some even referred to as Gods (Chaos), mainly for appearing too corporeal (all of these characters have quite mortal offspring). But here's how I define a Cosmic.

superdimensional Split Personalities

Illumina, Solaris, and presumably 'Gaia' (though this 'whole' is never shown) all display a noteable composite nature formed from 2 halves - Lumina Flowlight & Void, Mephiles & Iblis, and Dark & Light Gaia, respectively.

From these examples, I imply a few things:

• Each half represents a dark/light dichotomy (Lumina Flowlight & (dark) Void; Mephiles the Dark and the (light casting) flames of disaster Iblis; and the Gaia halves literally represent Life and Death, so I'll leave it to you to figure that one out).
  This further ties in to my theories on where Cosmics draw their power from, below.
• In each case, the halves also display some degree of mismatch in intellect from one another. Void orchestrates every complication in Sonic Shuffle on accident; Iblis is a bellowing beast; Light Gaia has missing memories.
  I theorise that the halves can be imagined as the 'two brains' of a dinosaur: one is the actual brain with far superior intellect, and the other is more like a nerve cluster that aids the cosmic in piloting its body of incromprehensible dimensions (even if this 'inferior' brain could pass for a normal person, such is the gap between our species).
  The two halves can also be pictured as the cosmic's superdimensional body passing through a lower plain of existence. If we imagine our 3D body passing through a 2D plain, to any theoretical inhabitants of that plain able to see us, they would witness us like a CAT scan, slice by slice as our form with depth, made up of infinite 2D planes stacked atop each other, passed through the singular 2D plain they inhabited. Our digestive system from mouth to anus may be percieved by them as splitting our form in half from a certain dimensional angle, and so we would appear as 2 entities to them while remaining one in 3 dimensions.
  I'm not sure yet if Cosmics are 4D (pictured as infinite 3D universes stacked atop each other, each representing an instant in time (a 0 dimensional point) along a linear timeline (a 1 dimensional line of stacked points)) or 5D (if you stack lines, you get length and breadth, 2 dimensions. Think of it as a plain that the timeline can spread out upon, diverting here and there along not just the X axis (from past to future) but also a Y axis (what is and what could have been), perhaps even splitting (tangent universe theory of time travel)).
  Don't worry, there are better explanations of theoretical dimensions above 4D elsewhere.
These two models may be somewhat contradictory, but they can be seen as unproven in-universe theories for the nature of Cosmics.

I owe a great deal of this theory to Cylent Nite's Sonic Expanse, one of the few large scale fanons I've read in any depth (and not much at that, since I could see how what little I read was skewing my interpretations, which I didn't like). Cylent's interpretation of the split was primarily a Jungian one (at least, what I read of it was), between masculine and femenine; Cosmics are probably too alien for pronouns, but be that as it may, I abandoned this interpretation because of the apparent contradictions in game dialogue. Lumina is referred to as female and Void as male, yes; but all others are exclusively referred to as male.
Still, credit where it's due. I conceived Sonic The Headcanon by myself, but Expanse was a big inspo to keep going. If Cylent ever reads this: 🫡

Shards

All cosmics have an associated 3 dimensional maguffin of limitless power, usually in the form of a gem. Gaia has the Emeralds. Illumina has the Perfect PreciousStone. Solaris has... nothing officially; I assign the Arks of the Cosmos to him (Each contain a gem, 5 gems matches how the PreciousStone shatters into 5 repeatedly, and I tie in the Babylonian lore closely to Solaris. In Blaze's dimension, there are similarly 5 gems embedded in the Scepter of the stars...).
But the Perfect PreciousStone is fused, what's up with that? Is the Master Emerald the equivalent? What about Solaris? Where do Argus and the End factor in... at all? Firstly, shards fuse when the cosmic is fused, as in Illumina's case (a fused Gaia would probably result in something like Sonic X's Planet Eggs). Secondly, the Master Emerald is Ancients (Chao) lore, it's unrelated. Thirdly, I'm just more mushy with Solaris' lore, and excuse it by the game being unfinished (see my adaptation).². And fourthly:

I've been neglecting 2 characters I refer to as Cosmics, Argus and the End, in this entire discussion (well actually I conflate the two as the same cosmic anyway, so one); you can thank Cylent again for me insisting that this dude is also in the same ballpark despite lack of evidence. Can you really blame me though? It clearly operates on a whole other level, yoinking civilizations and blowing up planets. We've just never seen its halves (nope, "progenitor" and "prophet" from Expanse don't hold sway here. starspawn in STHC)... or its shards... and its aspects are hard to guess... But nah, its absolutely a cosmic horror type of deal too; put it in the same basket; there's no need to overcomplicate things.

Oh yeah, aspects.

Aspects

Despite their apparently complete superiority to the affairs of the mortal species, Cosmics have been found to share an inextricable link to the supposedly lower beings; apparently psionic.
This is apparently less in the 'we thought them into existence' sense, and more in the 'psychic parasite' sense, though there is no indication that cosmics adversely affect 3 dimensional organisms they draw from the thoughts and feelings of for energy.

The main thing holding this theory up is Maginaryworld, the domain of Illumina. The cliff notes are that this is both a dream world ruled by a Cosmic, and more importantly, that it houses "dreams of those from other dimensions" - which I take to mean that the psionic impression created by the minds 3D creatures in this universe transends dimensions. Sounds like a good energy source for a superdimensional lifeform.

(Much) more circumstantially, is the conceptual themes to many cosmics. There's a dichotomy of Light and Dark for one (even if relative; Iblis' 'Flames of Disaster' still cast light, as contrasted with 'the Dark' of Mephiles). I could assign a conceptual dichotomy two each Cosmic I've mentioned; and I will:

• Illumina: sanity and insanity. Drawing directly from the dreams of earthlings has tuned her into the balance of good and bad mental health, I suppose. Note that this gives her a vested interest in the happiness of mortals; most cosmics who draw from our more abstract ideas end up caring a great deal less for us.
• Gaia: Life and Death. No prizes for guessing. This is why the Light and Dark energies of Gaias shards have such powers of destruction and preservation; also not their involvement in the cataclysmic cycle between Gaias Light and Dark halves, allowing life to flourish and then crushing it. Gaia as a whole draws energy, not from life on earth simply existing, but from its cycles of death and rebirth. It's in its interests to keep earth from becoming lifeless, but not to allow intelligent life on it to develop a cure for death.
• Solaris: Light casted by celestial timepieces, and the darkness of it's absence. Solaris is very involved in time travel, and in punishing it. He draws psionic energy from any 3D lifeform with the memory and perceptive organs to observe time flowing.
  Light and Dark really are part of every cosmic's aspects; the Sun and Moon Medals in Unleashed were linked to light and Dark Gaia. Light fuels life, and darkness brings the coldness of entropy. For Illumina's purposes, I dunno... it's scary. But anyway, Solaris gets close to drawing his energy directly from that most abstract and raw of conceptual nectars in the psionic realm; Light and Darkness. And this is why he is anchored to a star - One of the sources of Light and the forges of elements for the whole universe. Solaris is therefore an extremely powerful cosmic.

Oh yeah, anchors.

It's these dichotomies that drew my attention to Sonic Boom:Fire and Ice. However canonical it may be, Ragnium from that game displays an interesting contrast of heat and cold; I don't think it's a stretch to imagine it as some unknown cosmic's shards.

Anchors

Finally, cosmics as a rule all display a sort of 'thethering' to some 3 dimensional object beyond their shards, and these are invariably celestial in scale. As we have noted, they also relate to the aspects that fuel a Cosmic. Anchors have been observed ranging from a moon to a star, and the known anchors and the cosmics they relate to are listed below.

• Luna (Earth's moon) - Illumina (there's a minor theme of referencing the moon in Shuffle- the foolmoon forcegem, ; as well as just the circumstantial
• Earth - Gaia
• An unnamed star - Solaris

Starspawn

¹ I'm drawing a blank on anything before Sonic Shuffle, anyway. I don't think the secret angel statue in CD counts.

¹ here.