It recently occurred to me that there are more than a few similarities between these two Dunmer heroines. While Ayem's early life is not well documented, her years as the mother-figure of the Tribunal are relatively known to us. Likewise, there are two known accounts of Barenziah's life (that I am aware of), with a similar focus on her later, more public years as the queen and, later, queen-mother of Morrowind. Both rose to prominence as the public conscience of their people--indeed, both ruled over the same people at the same time. And both had very similar skeletons hidden in their closets.

Other than their position as queen of the Dunmer, most of this comparison focuses on those skeletons. Due to the importance of the Tribunal in Elder Scrolls lore, Ayem's secrets are well known. She was Nerevar's wife, in effect the queen of the First Council, and she grew in popularity from that time onward even as her husband faded into her shadow after his death. She, of course, took part in her husband's murder, after already betraying him in favor of Vehk. In return for her betrayal, she received great power, and created a public face of mercy as she reveled in her new station.

Barenziah's earlier life is better documented than Ayem's, but her later years are almost a smaller mirror-image of Ayem's. As queen of Mournhold, she ruled Morrowind on the Empire's behalf, alongside the general-king Symmachus (puppet or not, he was the closest thing to "legitimate" that the Dunmer had simply because he was Barenziah's husband). And, like Ayem, Barenziah was apparently bored with him. She betrayed him for the Nightingale, and by doing so she provided the Nightingale with great power not unlike Ayem's betrayal of Nerevar helped give power to Vehk. Because of that betrayal, and the unrest that followed when Jagar Tharn began the Imperial Simulacrum, Symmachus died. At this point, we find the single difference between these two: While Almalexia delighted in the power she wielded at Vivec's side, Barenziah (according to The Real Barenziah) pretended to give herself completely to Jagar Tharn only to oppose him. Barenziah acted out of repentence, while Almalexia acted out of vanity, and from this one difference we see two totally different endings for them both.

While this summary is rather lecturish, what I'm really trying to get at is a question. Was this intentional? My understanding of Daggerfall is rudimentary at best, but I do know that Barenziah makes an appearance there as queen of Wayrest. Was Almalexia present in Daggerfall lore, or was she added to history with the release of Morrowind? If she was mentioned in Daggerfall, was her story fleshed out at all, or was she simply some distant goddess of the Dark Elves (while Barenziah's history was already written)? I ask this mainly because I can imagine a dev meeting when Barenziah came up in the discussion and someone asked, "You know, what would have happened if Barenziah had given in to the power that Jagar Tharn offered her?" I can only imagine Almalexia as the response to a question like that.

To answer your question on the history of additions, Morrowind's god kings didn't exist until Morrowind.

It would make sense, considering that TES II was supposed to take place in Morrowind and roughly have Morrowind's plot, that Barenziah is modeled after Almalexia in terms of character and history.

After all, it's rather strange that the Queen of Wayrest is a dunmer.