http://www.imperial-library.info/content/fireside-chats:
M: Anyway, so, she's not in any way the female principle she is in the storming of the White-Gold or the Council of Skiffs. It’s 2700 years later, and she is indeed the queen of ancient times and when she appears she’s certainly not herself. She even talks here and she doesn’t sound [like she used to]. She's got remnants of how she talks in the Pelinal stories, but she's the mother of dragons here. That’s it.
Actually, there's quite a lot in that discussion that didn't seem familiar, but most of it had to do with Alessia. What I remember about Alessia amounts to a few sentences, mostly from TES IV: Oblivion and Knights of the Nine, about her association with Morihaus and Pelinal, about how she let the revolt against the Ayleid, became the first emperor, and received the Amulet of Kings as a seal of the covenant with Akatosh. Beyond that, that in the First Era, there was an almost but not quite monotheistic cult which called her Saint Alessia, which dominated a long-lived theocracy.
Are there some sources that offer more detail on Alessia's life, or are the details just scattered about here and there?