"The wise and good are outnumbered a thousand to one by the brutal and stupid."
Like most of the Louisiana branch of the Pendergast family, Cornelia lived in the Maison de la Rochenoire in New Orleans. After an angry mob burned Rochenoire to the ground, Cornelia's husband moved their family permanently to their estate of Ravenscry in Dutchess County, New York. Having inherited the Pendergast family's tendency to madness, she later poisoned her husband and two children, along with her father, mother and her brother Ambergris, believing them all to be possessed. She was subsequently confined to Mount Mercy Hospital for the Criminally Insane.
During her incarceration at Mount Mercy, her delusions manifested as a fantasy world in which she believed she was still in Ravenscry or Rochenoire, and the hospital staff were her servants. Her room was decorated sparsely with soft knickknacks (including a small needlepoint pillow from Kraus's Kaverns in Medicine Creek, Kansas, given to her by her grandnephew Aloysius), a set of valuable unframed antique paintings, and a collection of her favorite books, among them Cotton Mather’s Magnalia Christi Americana, Benjamin Franklin’s Autobiography, and Richardson’s Clarissa.
Aloysius Pendergast visited his great-aunt at Mount Mercy regularly, often seeking her counsel—particularly pertaining to their own family history—during his investigations. She was said to have been particularly fond of Pendergast's late wife, Helen. Vincent D'Agosta, at Pendergast's request, visited with Laura Hayward, posing as Cornelia's late brother, Ambergris; when he returned with Pendergast several months later, she recognized him, identifying him in her deluded state as Ambergris.Some time during the events of Fever Dream, the Mount Mercy staff notified Special Agent Pendergast that his great-aunt's condition had deteriorated. Cornelia had grown increasingly agitated and delusional, convinced that her brother Ambergris was coming for her to seek revenge. Eventually, she became violent to the point of needing to be restrained and medicated, and at the time of her supposed appointment with her brother, had a series of seizures and passed away abruptly.
- ↑ The timeline and location of Cornelia's serial poisoning changed from Ravenscry some time after the Rochenoire fire (Dance of Death) to Penumbra Plantation when Aloysius was a young boy (Cold Vengeance).