Lucille Verneuil ranks among the oldest surviving Shirogane, originating from a village near Bai Jin's mansion. She witnessed the Krogh village massacre, where her husband and son were murdered, a defining trauma. Lucille received the Aqua Vitae, an elixir of life crafted by Bai Yin, granting her extreme longevity, making her nearly 200 years old. To prevent the Aqua Vitae from dissolving and preserve its power against Automata, she deliberately concealed it within her daughter, Angelina Berneuil, ensuring continuous soft stone production vital for defense.

After an Automata attack killed Angelina during childbirth, Lucille raised her infant granddaughter, Éléonore, who unknowingly carried the soft stone. As Éléonore's adoptive guardian, Lucille became intrinsically linked to the core Shirogane legacy and their conflict. Her survival of the initial massacre and subsequent actions cemented her as a vital connection to the historical events involving Bai Yin, Bai Jin, and the origins of Zonapha Syndrome.

Later, Lucille actively joined Narumi Kato and Guy Christophe Rech in their pursuit of the Midnight Circus. Her participation demonstrated her enduring commitment to confronting the Automata and protecting their targets. Her advanced age and firsthand experience with the centuries-old conflict provided invaluable insight to the group.

Physically, Lucille appears as a tall, slender elderly woman with distinctive silver hair and pupiless white eyes. Her survival of the Krogh massacre and strategic concealment of the Aqua Vitae within her bloodline highlight her crucial role in preserving the means to counter the Automata, directly influencing the struggle against destructive alchemy and puppetry.