Damn, we should befriend Simendor. That sounds like a plot hook.
They all have plot hooks!
While you are likely to be using your own slightly modified/homebrewed version of Creation given the time frame this is taking place in, are you drawing on 3e for inspiration or should I review my 2e books (well, the PDFs) to get some sense of the people/orgs surrounding Ambraea. Her being Earth Aspect is interesting because last I checked that is the SE's aspect and Mnemon and V'neef re competing to emulate the SE (though this matters less pre-disappearance) so a third Imperial Daughter entering that competition (even if she has no idea it is happening) should be interesting.
In terms of like, how Dragon-Blooded work, the Realm/the Blessed Isle/the Heptagram, and things like how sorcery works, my primary source is going to be 3e. This is one of the areas where this edition has a lot of really good, high-quality coverage, and it was the material in
Heirs to the Shogunate (that picture I posted with this latest update included) that really made me want to run this quest. I'll still be selectively drawing on both older editions for odds and ends, like random spells that haven't made the jump, or especially demons and stuff, which haven't gotten nearly as broad an overview as they did in the older material. And obviously, yeah, I'm going to be filling in the gaps with my own material.
The Aspect of the Scarlet Empress is something that has been kept deliberately ambiguous in almost all Exalted material that mentions her, but apparently the long running intent in the line's development was that she was a Fire Aspect. Then when
Return of the Scarlet Empress came out and they gave her a stat block, she was made an Earth Aspect because Fire was too obvious or something. I am...
unlikely to look to that particular book for inspiration. 3e returned to being ambiguous about it, but they also very pointedly named their Dragon-Blooded book
What Fire Has Wrought.
Her children that we know of have been a variety of different Aspects, probably due to so few of them having the same father. By my count, of the ones who we know of, whose Aspects we know with a reasonable amount of surety, we're looking at... One Air Aspect (Jurul), One Fire Aspect (Sesus), Two Earth Aspects (Ragara and Mnemon, who explicitly had the same father), two Water Aspects (Peleps and Berit), and two Wood Aspects (Cynis and V'neef). She's had an unspecified but very large number of mortal and Exalted children, many of whom never founded a Great House of their own.
Canonically, there are at least five children of the Empress who are both Exalted and still alive: Ragara, Mnemon, Berit, Oban, and V'neef. Ragara is retired (and a man, and old as fuck), Oban is married to the matriarch of House Sesus and invests a lot of his energy into being the savvy social/political operator to her grizzled general, so he's not really a rival for the throne himself so much as his wife is. Berit is sulking in self-imposed exile after having an explosive argument with the Empress decades ago about mom not giving her her own House. So adding Ambraea to this mix like... both makes her relevant to the overblown family drama that exists between the siblings, while still not putting her anywhere near being a meaningful rival to either of her sisters who are matriarchs, at this early stage of her life at least, unless something really changes with her. It should definitely be interesting to see how she interacts with that mess when it eventually unfolds, though.