Edelgard had always loved reading. When she was young, she especially loved fairytales. She had forgotten most of them, but she still remembered one about a lord of the underworld feeding a heavenly maiden a fruit of the underworld so that she would stay and be his wife. Though she remembered it, she put down all childish thoughts once the war she had declared begun in earnest and her teacher was lost.
One day late in the war, shortly after her teacher had come back, Edelgard searched the library at Garreg Mach for any potential clues to aid in the assault Myrddin. In the process of doing so, she happened upon a book of fairytales with that story from her childhood illustrated on the cover. She related now, to that lord of the underworld.
Darkness had seeped into her soul and shadows would linger over her for the rest of her days. Her heart, too, belonged to a heavenly maiden. Since Byleth had come back, Edelgard had spent no small amount of time wondering if she was truly asleep during those five years, or if she simply couldn’t stay on this path of shadow for too long. Edelgard wondered how long it would be until Byleth left again, for in her mind it wasn’t an if, but a when. She worried the darkness that surrounded and permeated her would snuff out Byleth’s light.
Should Byleth leave again, Edelgard the Emperor would survive. The Empire would survive. The war effort would take a hit, but it would survive. Fódlan’s new dawn would survive, brought into being by sheer strength of will, were it necessary. To a degree, Edelgard the person would survive, thanks to her friends and classmates. Edelgard, the young woman whose heart had nurtured a love over the years, however, would not.
It was with these thoughts that Edelgard brought pomegranate pastries with her the next time her teacher invited her to tea. She knew this was a flight of fancy, feeding her that underworld fruit like this. But just the same, she hoped that the desire she dared not put into so many words would come across: Stay, please. Seeing her dear friend, guide, and keeper of her heart with lips stained pomegranate red eased her mind, and so became their habit.
Byleth’s father didn’t know many fairytales or bedtime stories when he raised her. So, when they returned to the Monastery, he used a book of fairytales and folklore to help her sleep. Of them was a tale of a heavenly maiden who was fed pomegranate by a lord of the underworld so that she would stay with him and be his wife. When El brought with her pastries made from that fruit with her to their teatime, the memory idly danced across her mind before they settled into easy conversation as if she hadn’t left her for five years.
When El made a habit of it, Byleth wondered if she thought herself to be the lord of the underworld trying to keep a shard of heaven in the shadows. El made no secret that she believed her path to be one drenched in darkness and that she feared this path wasn’t meant for Byleth and that she would leave again, this time willingly. She wasn’t wrong that this path wasn’t meant for Byleth, though.
Byleth was taught to be a vessel. Ostensibly, she was meant to be a vessel for Sothis, her... She still hadn’t figured out what her relationship was to Sothis now, whether she was simply the inheritor of her friend’s power, her reincarnation, or even some mix of Sothis and Byleth. Maybe she was all of those. In practice, before two became one and the flames of war engulfed the old order, Byleth was a vessel for Rhea’s hopes and dreams. She still was, to a degree, just one who had been upended and whose contents had been spilt out. Fundamentally, her path was meant to be one of guiding the Church and the faithful, and she chose the path to tear down the Church.
It hurt, seeing Rhea’s eyes light up with fury in the Holy Tomb, seeing the look of angry disappointment on Seteth’s face, seeing the look of betrayal on Flayn’s. Knowing that what was left of her family would never look at her the same, that there was a permanent rift between them now, even should they survive, hurt more. Yet she persists in pointing her blade and baring her fangs by El’s side at the institution that was her home for as long as she could remember, because there was no other for her that her conscience would abide. Her dearest friend told her to cut her own path, and so Byleth did.
With these thoughts, Byleth bit into a pomegranate tart, praying that her promise would come across: I’m staying, I won’t leave your side ever again. The look of ease and relief in El’s eyes and the slight smile on her lips told her that it was.