Component of the type VII secretion system (Ess) (Probable). Plays a role in Ess secretion during infection. Required for the efficient secretion of EsxA. Required for abscess formation and staphylococcal persistence in host tissues (PubMed:21278286, PubMed:24033479, PubMed:27795322). Possesses a toxic DNase activity that is modulated by EsaG by forming a nuclease toxin-antitoxin pair. This nuclease toxin targets competitor bacteria (By similarity). Interacts (via C-terminal) with EssG; this interaction blocks EssD activity (By similarity). Interacts with EssE (PubMed:27795322). Released from the cell in a form that is immediately active while EssG partner protein remains in the producing cell where it may potentially serve further protective functions. Deletions mutants are defective in the secretion of EsxA, EsxB, EsxC and EsxD. Belongs to the EssD family.