Re-reading the Anuad and the Monomyth again and it feels like there's some confusion around exactly what happened in that event. I know this is the normal state of affairs for TES, but it never really seems to get discussed.

With the Amaranth discussions, there was the frequent assumption that Nir was the witness part of the Anu-Padomay-Nir enantiomorph, but according to the Anuad, it is Nir's death through childbirth that creates the Twelve Worlds of Creation. She's also missing from the Monomyth accounts, a la Lorkhan, whose heart was torn out at Convention. It sounds to me like Nir wasn't a witness in the sense required for an Enantiomorph, but forms another part of the process. Exactly what part I'm not sure, as the Rebel who becomes King doesn't seem to fit her role elsewhere, although it is possible that her absence then defined Anu's actions in much the same way as Lorkhan's affected Mundus...

I'm thinking aloud at this point, but does it make sense? Do we need to re-evaluate the original enantiomorph?

Because they aren't telling the same story. Not at all.

I don't know how many people here remember the Amaranth Hunt, I myself wasn't there for it, but it holds the answer to this discrepancy you note. There is too much for me to recap here, http://www.gamesas.com/topic/1451586-summing-up-the-amaranth/

The Anuad is not the story of this Aurbis, but rather the prior one. At the end of the Anuad, Anu, stricken with grief at the death of Nir, flies into the sun to be alone. His Love makes of him an Amaranth, and in the total sensory deprivation of being inside the sun, he Dreams (or hallucinates) a new world - the Aurbis of TES, and he populates this Dream with characters that are similar to but not identical to the ones he knows. A dream-version of himself, as well as Padomay. Notably, there is no Nir in his Dream, which is why "Nir" never appears in the cosmology of TES outside of the Anuad specifically. No one ever felt like addressing that uncomfortable discrepancy because before the Amaranth Hunt, we simply couldn't.

Another tip-off is the whole "Twelve Worlds of Creation." What?

Since when is there ever twelve of anything in TES? The number has very little to no significance in the cosmology of our Aurbis: there aren't twelve Aedra or twelve planets or twelve Daedric realms. So where does this Twelve Worlds of Creation come from? The prior Dream. That was the geography of Anu the Amaranth's original universe, not ours.

There's a reference to twelve worlds in Tsaesci creation myth.

"There was the Striking, and the Egg was split into twelve worlds, one for each serpent who had a name, and the names of the serpents were alive and coiled into themselves and became more eggs, for names are self-maters, and the Naming went and went. According to the calculations, the random sequence learned very cunningly that fragmentation reserved itself to the left eye. Variation realms were the evidence needed.

There was the Biting, which broke the twelve worlds and their name-eggs, and the Biters chewed new names of the lesser serpents until soon death was known to the smallest and your alphabets disappeared but ours did not. The state of rest became worthy of blame, however segmented, so heat was wasted across the right eye. And in mercy we gave to you language that was dead yet walking if you used it, which you did, though transient food-forms became problematic."

Later on there's also a reference to the "twelve-to-one talking unsense".

Months, man. Months. And something to do with the Magna-Ge probably. The night sky of Mundus, as shown by the Dwemer orrery.