I just read 'Journal of the Two Sisters' · 2:58pm Apr 19th, 2015
And whoooo boy. There is so much good stuff as far as fodder for creating an Equestrian and pre-Equestrian timeline, as well as a timeline for Star Swirl, Celestia and Luna, and the three pony tribes. Looking over my fic, I don't think I've written myself into too much of a corner, now that I know these details. I think I'll just have to do some minor tweaking here and there to establish what age we're in when the Sirens were fillies, and how all the ponies were living (or not living)