My History of the Multiverse

it needs the inverted commas taken out, after that it worked fine for me

Yeah, I like the contrast between the two myself.

The reason I go with a Inner>Prime>Outer theory is the growth and complexity I see emerging in the Outer Planes as Primes became smarter. At first all you had is unthinking proto-gods and proto-elementals wandering the planes and all they really understood was creation, inaction, and destruction (Primal Law, Primal Neutrality, and Primal Chaos), but after a while, mortals started popping up one microbe at a time and suddenly there was this notion of help (Primal Good) and Harm (Primal Evil) and from that notion emerged the Baernaloths and whoever the Celestials evolved from. Of course, the Baerns and their enemies had been dreamed up by about the stupidest creatures you can imagine back while most of the spheres were still forming, so while they may not be older than the Prime, they are older than most of the Crystal Spheres. Despite being thought up by mold, the Baernaloths were able to grow and adapt, after all, belief is not bound by the same limitations the physical world is.

After a while, the simple notions of create and destroy and harm and hurt were refiend by more complex organisms until the Outer Planes split again and new exemplars like the Obyriths and Ancient Baatorians emerged on the planes. These beings represented animalistic emotions such as fear of the unknown. And there was fighting and manipulation on the Outer Planes more millenia, but the Prime moved on, and finally sentient mortals appeared. First they concieved of basic ideals like Benevolence and Malevolence (while later coalesced into Guardinals(?) and Yugoloths) and from there sprouted other ideals like liberty (Eladrin) and Tyrany (Baatezu). And that's how two races of exemplar became twenty.

FWIW I mentioned the Temporal Energy plane recently in Dragon, putting it as a demiplane like it was in 2e, but adding that it was sometimes referred to by the name it had in the 3e MotP where it was included as an optional plane.

Nope, the Tanar'ri were created prior to that period, but very much as second-class fiends in the Abyss, servitors to the Obyriths. It was the Eladrin whose attacks against the Obyriths allowed the Tanar'ri to supplant the older fiends and rise to dominate the Abyss. We don't however know if before this point the Tanar'ri or Eladrin were created first on their respective planes (the Eladrin are a dead spot in planar pre-history at the moment).

I've come to accept that the first Baatezu were the result of a corruption of some of the primordial LN outsiders, so at its core there's a bit of history in the FC:II myth. But in good despotic historical-revisionism fashion, there's no need to mention the Ancient Baatorians that were already there in Baator before the Baatezu first arrived.

Most of my stuff is written prior to FC:I reworking the truth of the Heart of Darkness myth, though I'm probably to blame for pimping my ideas to the authors of the FC:I which made them tackle a mention of the Baernaloths and the 'loth creation myth in the first place. So my original ideas had the Tanar'ri being spawned by the 'loths/baern dumping tainted larvae into the primordial Abyss, and at least some of the early Tanar'ri being spawned as a result of the literal rape of Pale Night. The authors seem to have run with that last idea a bit, and it inspired the line in FC:I about Pale Night potentially being the literal mother of the Tanar'ri race as a whole.

But as it stands (and my future stuff as it addresses the lawful side of the lower planes will incorporate this) the Baernaloths/General of Gehenna appear to have created the Ancient Baatorians and the Obyriths, however the legends of these events as told by the yugoloths rewrite history and present the Baatezu and Tanar'ri in place of the older fiends, probably because it's politically conveniant in the current era, and if the status quo changes, so will the myth that gets leaked out from the 'loth history books. Some of the 'loths might even believe their own falsifications on history, and their elders are probably too amused by this to tell them.

I think I would prefer for the 'earliest of ages' to remain somewhat mysterious -- and probably also to vary from one DM's campaign to another.

The yugoloths certainly believe that they are the oldest of the fiendish races -- but the tanar'ri and baatezu also each claim to have come first.

I also think it possible that the appearance (and possibly even caste systems) of the fiends may have changed radically over incredible periods of time. When that ancient saurian race (Old Ones) were the dominant race of Sigil, would the fiends have resembled what they do today? Same goes for the days of the Illithid Empire, or times even more unthinkably far back in the past. In my opinion, the current 'true form' of an arcanaloth/ursinal/lupinal/etc. does not predate the existence of jackals, bears, and wolves in the Multiverse.

Over extremely long spans of time, planeborne would be (if we continue to follow this theory) fundamentally changed by major changes in mortal belief. I'm pretty sure Faces of Evil even hints at this -- one thing that worries the 'loths is the possibility that the concept of Evil may change.

Zimrazim's allusions to an "ancient saurian race" sounds like either the spell weavers (3eMMII) or, more likely, the sarrukh (Serpent Kingdoms). There's more on the the idea of a multiverse before the ascension of mammals at the Musee Arcane.

There isn't much on them -at all-, and as far as I know it's only that story of mine that links the original CG race of Arborea to the Infinite Staircase. The entire idea of a CG progenitor race is really just a derivation from the Baernaloths, and the assumption that there might have been races of proto-celestials before the current celestial races came to power. The utterly ancient ruins on Pelion are what makes the idea of proto-CG celestials so yummy, and perhaps also the titan-esque beings upside down and hanging in that one layer of Carceri. I spun a few of those ideas into something coherent, but it's not something that's necessarily supported overtly in the sources.

I haven't had a chance yet to fully read through your timeline yet, but I'll make some comments when I do.

I like the theory that Archons and celestials in general derive from a mostly CG race we know as Aeons. This race produced all the raw materials of the Outer Planes. They influenced the nature of the more material planes emerging or re-emerging from the Deep Ethereal. They even helped shape the Lawful entities who would set the current boundaries of all the planes, though opinions differ as to how much of this the Aeons intended to happen.

Then came the Far Realm incursion that produced the Illithid Empire (or, as the mind flayers prefer to call it, the First Illithid Empire). At some point after this, the Aeons chose to withdraw from their home in Pelion. They knew that in order to stay they'd have to kill not just mind flayers but imitation illithid empires like the Imaskari as well. Not wanting to do that, and not wanting to prevent it by imposing their own law on mortals, they vanished from history. Nobody knows where they went. Some ancient songs of the elves suggest that Morwel's Court of Stars might still act as a bridge between Pelion and the hidden realm of the Aeons.

We stole the name Aeon from Gnosticism, which also supplied "archon" originally. Both come from Greek. An Aeon created the first Archon without meaning to and then regretted it, hence the Chaotic Good alignment. I think I stole the rest of my version from Tolkien. Stealing from multiple sources is "research".

I believe Shemeska's referring to the hanging giant bodies that form the basis for the town of Gallowshome on Colothys, mentioned in the "Players Guide to Conflict". This indicates that the giants are part of a long dead race which predates recorded history and that Fiends aviod the area if possible. It also mentions that the rotting giants might not actually be dead despite their slitted throats- just sleeping.