*gasp* I knew it! …oh, wait, I think I knew this since the last book.
I’m only halfway through The Golden Lily and I realized Trey is a vampire hunter…or whatever they are calling themselves. He showed up extra beat-up one day (same day he missed class) and during the attack the guy that pinned Sydney down recognized something about her. At first I thought it was that her tatoo was visible and he was surprised that an alchemist was there but maybe it was Trey and he recognized her!…or the cousin. He did meet her once and I wouldn’t be surprised if it was a family business kind of thing.
Just wanted to share this realization.
And also, right after he leaves, she begins to think about his bruises and coincidentally (not really) Adrian texts her about vampire hunters possibly existing.