Kronya is actually Monica and the Von Ochs house was Agatharian run (they mixed in with normal people over time so they actually are less visible), and based on this, I can safely hc that she's a little bit older than Cethleann but not as old as the other 3 Saints
Their technology was actually meant to put less strain on Sothis, in order to thank her but it fucked up bc someone killed some innocents and it all went to shit
Sothis actually does have her own preferences that don't align with Byleth, including an extreme obsession with Guac
TBH, most of my current headcanons so far are in my fics: https://archiveofourown.org/works/17833226 (starts as heroes, adds 3H later on) and https://archiveofourown.org/works/21611611/chapters/51533626 (a Christmas fic that I'm gonna be updating every year around that time)