The story begins when Lia de Beaumont's corpse is found floating down a river in a casket marked 'psalms.' The mystery of who killed her and why is the motivation for the plot.
She was a member of le secret du roi, serving King Louis. Although she remained loyal to the king, Robespierre, her partner and fianc�, did not. He stole the book of Royal Psalms. King Louis murdered her for reading it, after luring her into a trap with a fake letter from Robespierre.
Lia was popular around the court at Versailles and within other royal courts.
- She was Auguste's favorite teacher (D'Eon:Lia)
- Anna called her a friend and mentor (D'Eon:Lia)
- Durand knew her well, although the nature of their relationship is unclear
- She went to England with Robespierre and accepted his proposal of marriage. Later, she rejected him when she found out he was her half-brother. (Out of Deepest Love and The Word)
- Teillagory was her fencing instructor
- Robin knew her well enough to be 'sure' it was her possessing d'Eon (Follower fo the Revolution)
- d'Eon's older sister
- served King Louis loyally as a member of le secret du roi under Broglie
- Queen Marie seems to have spent some time conversing with her as well (Follower of the Revolution)
- allegedly saved Empress Elizabeth from an assassination plot, and gave her the idea for the crossdressing masquerade ball
- helped to bring Queen Mary back to life by putting her soul in her sister's body
Lia uses both fencing and the magic of the psalms to defeat enemies. Her swordmanship is very good, and also distinctive enough that Teillagory can recognize it (Sword of Indignation). She recites psalms as she fights, and sometimes the spells are even visuallized as glowing words. She uses magic to gestroy the canine gargoyles in Gargoyles and to break the spell on Robin's arm in Robert Wood's Briefcase.