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Tear Jerker: Anti-Cliché and Mary-Sue Elimination Society
Adrian's Final Speech letter to Tash left in the Codex of Index is KING of this. My god. It's addressed to everyone he cared about and was close enough to...and reflects on the things he'll never get to do, in a sense.
Rhia's death shocked many to the point of this.
Adrian telling the story of his past to Tash. (That is...until it turns out to be false.)
Willowe reconciling with Adrian reveals there are Tear Jerker-worth moments here.