Forms a proteinaceous shell that encloses the viral DNA and compartmentalizes proteins and DNA during viral infection (PubMed:28813669). This shell is the site of viral replication, with the proteins involved in DNA replication localized inside the compartment (PubMed:28813669). Provides a surface for docking of capsids during packaging (PubMed:28813669). In infected host cells assembles as a nucleus-like structure in the host cytoplasm. Belongs to the Phikzvirus gp105 family.