Announcement: The Heroes of Legend now has a TV Tropes page! Please visit the tropes page and add anything you can think of! I won't post a link because FF doesn't allow you to link to an external site, but it shouldn't be hard to find.
This chapter is more or less irrelevant to the majority of the story; I'm just writing it to get the awkwardness between Rhea and Jeralt out of the way.
"And we're going to have to stop here," Kronya said. "Much as I'd like to keep going, I have to send a report to Thales. Since Solon is dead, I need to send in a report he'll believe so he doesn't think anything is wrong. Edelgard and I made a plan to assassinate him. If he catches on that something's wrong, things get messier."
"That would be a problem," Rhea agreed. "Go send your report."
"Right," Kronya said as she left.
Once Kronya had left, Jeralt turned his gaze to Rhea. "All right, Rhea. No more secrets, no more lies. I've waited long enough. What happened on the night Byleth was born?"
Rhea nodded. "Very well. I will explain what happened, but we should go somewhere more secure."
The four of them left the room and went to one of Rhea's secret, secure meeting rooms. "Now I will explain everything."
Seteth looked at her. "Should I leave?"
"No," Rhea said. "No, you should stay. This does concern you as well."
She took a deep breath. "There is some context that needs to be addressed. I need to explain Sitri's origins. Jeralt, do you remember the influenza outbreak of 1139?"
"I guess so," Jeralt said.
"Well, during the outbreak, I treated several orphans who had fallen ill. Most of them recovered, but despite my best efforts, one of the orphans, a young girl, succumbed to her illness," Rhea explained.
"O-kay," Jeralt said, clearly not understanding where this was going.
"I offered to arrange for the orphan girl's burial," Rhea continued. "I had a coffin placed in a grave. But the coffin was empty. Instead of burying the orphan girl, I placed the Crest Stone of the Progenitor God in her chest, and used both magic and technology of ages past to restore her vital functions."
"You performed necromancy?" Seteth asked, shocked and horrified.
"Not necromancy," Rhea insisted. "Yes, what I did had far too much in common with the practice, but I made no attempts to return poor Jenny's soul to her body. Make no mistake, Sitri was not resurrected that night, she was born."
Byleth held up her hands. "Hold it, we're talking about the Crest Stone of Sothis, the same Goddess that Nemesis killed?"
"Yes," Rhea confirmed. "My intent was for the Goddess's soul to be the one to enter the girl's body, but that wasn't what happened. All the same, Sitri was my responsibility, and I quickly came to treasure her greatly. I ensured that she would be able to live a full, fulfilling life, and in time, she fell in love with you, Jeralt, and eventually became pregnant.
"However, Sitri was always frail, and her pregnancy was very difficult. I tried my hardest to save their lives, but it became clear that neither Sitri nor Byleth would survive. As she lay dying, Sitri begged me to remove her Crest Stone and place it in Byleth." Rhea looked like she was fighting back tears. "I did as she asked."
"Okay," Jeralt said, also clearly distraught. "That doesn't explain why Byleth never cried as a child."
"I can't explain that," Rhea said.
"Why not?" Jeralt asked.
"I can't explain why she never cried, because I don't know why. I was trying to figure out why when you left Garreg Mach."
"I see," Jeralt said. He sighed. "You could have just told me. I wouldn't have held it against you."
"I am sorry I didn't," Rhea said. "You were one of the dearest friends I ever had, Jeralt. I was a fool not to trust you."
"It's not entirely your fault," Jeralt said. "If I had confronted you and given you a chance to be honest with me instead of just running away, things might have been different. You were my closest friend for hundreds of years. I should have known you well enough to know you weren't up to something terrible."
Seteth cleared his throat. "Rhea. You know I love you. You're one of the few family members I have left. So I hope you don't take it the wrong way when I ask what the fuck were you thinking? Yes, technically what you did wasn't necromancy, but do you think most people would see the distinction? If anyone found out..."
"I know I made a big mistake," Rhea cut him off. "I will not apologize for it, because Sitri was born from it, but I understood afterwards that I had gone too far. I decided shortly after Sitri's birth that I would not try to resurrect the Goddess again."
Seteth took a deep breath. "Well, at least you learned your lesson."
Rhea looked at Byleth. She wasn't lying. She hadn't tried to resurrect her mother again, nor would she. But she suspected she might have at least partially succeeded by accident. After all, she knew Byleth did have a connection to the Goddess that Sitri had lacked.
The only question was what that connection was.