PackagesH.P. Lovecraft’s stories (e.g., The Shadow over Innsmouth , The Lurking Fear ) often feature rural families that have practiced incest for generations. Lovecraft was obsessed with "degeneracy." In his fiction, incestus ad infinitum produces not just physical mutation but a breakdown of the distinction between human and monster. The ad infinitum is spatial as well as temporal: the inbred family becomes a singular, crawling biomass rather than a society.
The phrase serves as the family motto for the Davenports, the fictional aristocratic family at the center of the film Fackham Hall (2025) . Fackham Hall (2025) - IMDb incestus ad infinitum meaning