- The reveal that Noah is dead. Especially when you find out how it happened and the person who killed him was supposed to be his best friend, and the realization that Noah died for nothing.
- Ronan's guilt and self-hatred in The Dream Thieves. The kid blames himself for not finding his father's body until it was too late, has frequent nightmares about being killed (which, given the nature of Ronan's dreams, essentially means he's dreaming about killing himself), is convinced he's an unholy person and is going to hell, and on top of it all is starting to realize he's gay, which can't be fun for an Irish Catholic person in the Bible Belt. It really says something that the most dramatic moment of the book isn't Kavinsky's death but Ronan realizing he doesn't hate himself anymore.
- Gansey, Ronan, Adam, and the Gray Man are all clearly suffering from untreated PTSD (Gansey from his own death as a child, Ronan from his father's death and the loss of his family and home, Adam from his parents' abuse, the Gray Man from his brother's torture), and it's awful seeing them struggle through panic attacks, dissociation, and all-out flashbacks with no one helping them.
The Raven King (unmarked spoilers)
- A recent excerpt from the beginning of The Raven King reveals that Gansey has known throughout the entire series that he was going to die within the year. He has gone about his life with that knowledge, declaring his intention to ask Glendower for Noah's life, and not to change his own fate a second time.
- Ronan's reaction to his mother's death in the last book. He doesn't lash out, get angry, look to his friends and new boyfriend for comfort, or even cry more than a couple of tears. He just... sits in his car, staring at the street, waiting for Gansey to tell him what to do next. Adam chooses to sleep in the passenger seat so that Ronan won't be alone, but even then, Ronan just sits there motionless for hours.
- Noah's one POV chapter in the series, near the very end of The Raven King, ends with this excruciating Call-Back to a repeated line of his in the very first book:"Good-bye," Noah said. "Don't throw it away."He quietly slid from time.
- The entire chapter is a massive tear jerker, particularly The Reveal that he was the one who spoke to and saved Gansey, but the surprisingly upsetting part is that Noah retains just enough of himself to know that he played skip rope at some point, but he can't remember who with or remember the exact instance.
- The discovery of Glendower—what we had thought would be the great, climactic triumph of the series—turns out to be one of the most heartbreaking moments of all four books. Glendower is dead, and has been the whole time. He was never put in magical stasis, and it's possible no one ever intended to do so in the first place. The discovery puts Gansey into a brief Heroic BSoD, which he snaps out of by sobbing his utter heart out in grief for his king and for every version of himself that he'd been over the past seven years. Worst of all, he mentions that he can't remember the last time he cried.
- Even after 4 books to get used to it, Gansey's death is still heartbreaking. Luckily, he got better.Right after he spoke, she held him like a shouted word. Love, love, love.
- Cabeswater's Pre-Sacrifice Final Goodbye with the gang, particularly Adam.And finally, the magician's wistful regret twisted through what remained of the trees. Without this, what was he? Simply human, human, human. Cabeswater pressed leaves against his cheek one last time, and then they took that humanity for the life it was building.
- In the Opal short story, it's revealed that despite everything, Adam doesn't get into his top choice college. Admittedly, it leads into a Heartwarming Moment of Ronan and Opal comforting him, and we know that he does end up getting into another college, but it's still painful after four books of Adam working himself to death for his education.
