Something about Baghra refusing to teach or meet with David because he reminded her too much of her father.
Something about Baghra's mother refusing to touch or care for her, because she was one of her father's abominations.
Something about Alina having more power over the The Stag's Amplifier, despite her not being the one to kill it. It being the only amplifier David connected to her.
Something about "Morozova was the Bonesmith, one of the greatest Fabrikators who ever lived, and a man who tested the very boundaries of Grisha power, but he was also just a man with a wife." Well David was chosen to fuse Alina's amplifier to her collar bones because he was a powerful Durast. Something about Genya being David's only distraction from his work.
Something about the last name Kostyk having Salvic ties to the word bone. Something about the name David having Hebrew roots to mean "Dear" so you could interpret his name to literally mean Deer Bone
Something about Ilya Morozova having healing abilities, and something more about David falling in love with A Tailor who bled the line between Fabikator and Corporalki.
Something about David telling Genya, with blacked or corrupt scars running over her body and telling her she doesn't need fixing, well Ilya Morozova never tried to fix Baghra, a making of his own corrupt magic (merzost)
Something about David being distracted by his work, and not noticing Genya for the majority of the first book..something about Ilya being absent and consumed by his work.