Well lookie there, cult initiation tactics perpetrated by checks notes worlds most violent cult. That checks out.

Any chance it’s “The Thieves of Ostia” by Caroline Lawrence? It’s Roman not Greek, but those can be pretty similar

Sounds a lot like “Becoming Human” by John C. Wright. Any other details come to mind? Or titles that you’ve ruled out?

Baby Journal could use an more detailed About page. It looks like it’s a shared space for families to post/talk about their kids in digital saftey. What an awesome idea! Well done!