Three myths on the Coming of Chaos are given to us by canonical sources. One is a tale told by Markus Fischer (henceforth referred to as MF), one is an excerpt from a source known only as the Obernarn Stone (henceforth OS) and the third is the myth Lord Ulric and the Making of the World (henceforth LUMW). The OS gives a pretty long list of the Gods involved in the Coming of Chaos, but is pretty sparse in details about what they actually did (most attention is given to Taal, but even there OS doesn't go into a lot of detail). MF gives a relatively high amount of details on the exploits of Hoeth/Verena, but it barely mentions other Gods. In some way LUMW is the best of all worlds, as while it's obviously focused on Ulric it also tells us about a number of other Gods and it gives a decent amount of detail on the events that took place during the Coming of Chaos. This is the myth which tells of Ranald escaping and burying Himself beneath the desert sands, and of the three it's the longest one by a very wide margin. Unfortunately, it's also the only one that contains very clear falsehoods.
Now just to be clear, it's reasonable to suspect all the myths of being written by unreliable authors driven by motives such as painting some specific God in the best light, or of containing mistakes or mistranslations, but LUMW is especially bad in this regard. The OS is a stone of unclear origin and the MF tale is a story "from the Asur", but LUMW is from "an ancient collection of legends which is now a religious relic kept in the Temple of Ulric in the city of Middenheim", which might mean that there's reason to suspect that the story has been modified and interpreted to fit the Cult of Ulric's narrative. The Gods mentioned in LUMW are precisely the pantheons that are currently worshipped in the Old World - all of the Old Pantheon plus all of the Classical Pantheon save Myrmidia, which fits the Gods currently worshipped in the Empire a bit too neatly. The most clear-cut reason to suspect it is the fact that LUMW provides an origin story for the Skaven and a story about how humanity learned to work metals, both of which are contradicted by other reliable sources. It's also clear that LUMW doesn't give us a full picture, as it's mentioned that some dragons and unnamed lesser Gods were allies of the Gods and fought with them against Chaos but that isn't expanded on anywhere else in the tale.
What I want to focus on most is two ways in which this myth contradicts the other myths. First is the matter of the cast of characters. The list of Gods that appear in LUMW has a lot of overlap with OS, with two crucial differences. Three Gods that appear in OS aren't mentioned in LUMW, those Gods being Sotek, Margileo, and a certain 'Flaming Phoenix' who isn't named but from context is almost certainly Asuryan. Additionally, there's one God that's mentioned in LUMW but not in OS, Rhya. Both of those changes are ones we can expect from a myth written or collated by Imperials, as the three Gods removed are either non-Imperial or in the case of Margileo a non-major God in the modern Empire (Margileo is worshipped in Averland but is extremely minor) while the one added Goddess is an important one in the modern Empire and so clearly "should" be in this kind of myth.
Second is the matter of Verena's sword. In both LUMW and MF Verena picks a sword in response to the Coming of Chaos, but the origins of that sword are very different. In MF the sword is an Old One artifact called "Tlanxla's Sword of Judgement", cleverly stolen from Daemon God called Ulgu. In LUMW the sword is actually Morr's sword, which Verena takes when Morr refuses to respond to the Coming of Chaos, thereby shaming Him and the other Gods into action.
What I want to claim in this post is that a careful reading of the myth actually provides decently good evidence that these two discrepancies are later additions or edits made to the original myth.
Regarding Rhya, LUMW starting with a "dramatis personae" listing the Gods that will be involved in the story: Taal, Rhya, Manann, Morr, Verena, Ulric and a bit later Ranald. Shallya isn't mentioned yet because in this myth She is only born after the Coming of Chaos. Here is the first mention of Rhya in the tale:
"Father Taal and Mother Rhya tended the things of the land, and their son Manann was master of the things of the sea. Morr was king of the darkness, and Verena the queen of the light, and so all was in balance. In the high summers, Lord Ulric, brother of Taal and prince of the snow and ice, had no realm to tend to, so he had taken to walking the earth and the sky and the stars to seek adventure."
Later Ulric comes back from the north pole to tell everyone of the incoming Chaos incursion, and the story tells how He goes around asking each God for help, and all of Them ignore Him save Verena:
"His brother Taal did not believe that there could be another world beyond his, and Manann had no care for things of the land. Great King Morr believed Ulric's story, but did not see a great danger -- certainly it was nothing Ulric himself could not handle. Ulric despaired, knowing that even now the Chaos hordes must be pouring into their world, led by their own great and hideous gods, ready to destroy all they had made. Finally, he appealed to Queen Verena, and in her wisdom, she saw that the danger was indeed very real and very great, and that these fiends would destroy all of the Beauty and Reason she had created."
Did you notice who is missing? Ranald isn't there because He escaped, and Shallya isn't there because She wasn't born yet, but where is Rhya? Rhya is mentioned exactly once more in the story, when the Gods fight Chaos:
"Behind him rode King Morr, bringing the darkness of death, and Queen Verena with her sword of light, and Father Taal with the fury of the lion, and Mother Rhya with the strength of the mother bear, and Manaan brought the sea forth into the field[...]"
That's it. A single offhand mention when the Gods are all listed, a single offhand mention when the Gods are all described fighting Chaos, and nothing else. This is exactly how I would expect the myth to look if Rhya was a later addition: she's added in sections where all Gods are listed right after Taal, but doesn't actually play any role in the story beyond that. Hardly definitive proof, but along with Her absence from the Obernarn stone I do think there's reason to be suspicious.
As for Verena's sword, here's the first mention of Verena taking it:
"She swore that even if her husband would not act, she would, and she took up her husband's sword and rode out to battle with brave Lord Ulric."
And later, when the Gods are fighting Chaos:
"Behind him rode King Morr, bringing the darkness of death, and Queen Verena with her sword of light[...]"
Do you see the problem here? The sword is supposedly Morr's, yet it's described as Verena's sword of light. At the very start Morr is described as king of darkness and Verena as queen of light, so why would Morr's sword be a sword of light? In fact, a bit later in the myth it's said that Morr wasn't much of a warrior at all:
"Morr was no great warrior, and Ulric had proven his wisdom in seeing the danger, so Morr gave over to Ulric command of all the gods' forces, and Ulric thence became the god of battle."
which makes one wonder why He had a sword at all. Again, there's no hard proof here, but it's not difficult to imagine reasons for why LUMW might get this wrong. Possibly it's because the Ulricans don't want any other God to have a martial aspect to Them, especially not a woman (Myrmidia is absent from this tale, after all). Maybe it's a misunderstanding or a mistranslation or a different interpretation of the story MF tells - Hoeth stole a sword from the Lore of Shadows, Verena steals a sword from the King of Darkness. There's actually another part later in LUMW which involves Morr and which I strongly suspect to be a similar misunderstanding/mistranslation, but I'll leave that for a future post which may or may not ever actually get written.
Anyway, this was a lot of words on a few very minor points, but hopefully someone will find at least some of this a bit interesting.
*I had intended to title the last section of that post "Lord Boney and the Fanfic of the Gods", so seeing the title of that sidestory was even more of a mindfuck than it otherwise would've been.