This is a breakdown of Eirika's character and growth over the course of Fire Emblem 8. Much thanks to @Icelerate for co-writing this (he wrote the green parts) and @Yexin and @BergelomeuSantos for providing screenshots. This will cover the entirety of the story, followed by Eirika's Endings and Supports. Also, I got permission from @eclipse to split this up into multiple posts if I was having problems and SF gets really laggy when making long posts, so I hope you allow these consecutive ones!
Edit: I can't edit the other posts so I've moved Act 3 to this one (alongside making changes to Chapters 14-16 and 21). There's also a poll!
PART 1: ACT 1
PART 2: ACT 2
PART 3: ACT 3