Moth only appears in the fourth book, "Once Upon a Crime". In this book, Moth poisons the King, Oberon, and then joins the Grimms as they hunt for Cobweb (the King's doctor) who theu believe commited the murder. However, Sabrina realises that Cobweb is not the murderer when his actions of saving them do not match the suggestion that he killed Oberon. Moth, therefore, kills Cobweb by shooting him out a cannon from a puirate ship.
Moth has a history with Puck as he was once engaged to her and he didn't like her! His father, therefore, threw him out of Faerie for disobeying his orders to marry Moth. Mothn is very jealous of Sabrina when it is shown that Puck has feelings for Sabrina by making her his "protector" when he is inside the cacoon, showing he trusts her more than anyione else. Moth is enraged and tells Sabrina that she (Moth) should have had that privilage. At the end of the story, she confesses her murders to Sabrina, whilst poisoning her, believing that once Sabrina is gone, Puck would make her his Queen. She even calls him "my love!" Needless to say, her plan totally fails and Sabrina is rescued by a fully resored Puck.
Moth is described as quite pretty and she wears a dress make of material that resembles spiders webs. She look down on most people and refers to others as "commoners". Nobody likes her.