Maiza Avaro's younger brother, Sylvie Lumiere's boyfriend, and a passenger aboard the Advena Avis.

Spoiler

After he and Maiza became complete immortals, Maiza told him half of the Grand Panacea's knowledge—knowledge which Szilard Quates obtained after devouring Gretto in his sleep. Gretto thus was the first casualty of the 1711 generation, and his murder the prelude to a massacre which would claim twelve other passengers that night.