Component of the type VII secretion system (Ess). 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 (By similarity). Possesses a toxic DNase activity that is modulated by EssG by forming a nuclease toxin-antitoxin pair. This nuclease toxin targets competitor bacteria (PubMed:27723728). Interacts (via C-terminal) with EssG; this interaction blocks EssD activity (PubMed:27723728). Interacts with EssE (PubMed:27723728). Released from the cell in a form that is immediately active while EsaG partner protein remains in the producing cell where it may potentially serve further protective functions. Belongs to the EssD family.