Head of Starfleet Security who was secretly a half-Romulan leader of the Zhat Vash working to wipe out synthetic life.
Commodore Oh, played by Tamlyn Tomita, is head of Starfleet Security in the late 24th century. She presents as a Vulcan officer but is secretly half-Romulan and a leading figure of the Zhat Vash, a Romulan secret society dedicated to destroying artificial life.
Oh is behind much of the conspiracy in Picard's first season. She is the contact in the Federation for Narissa, who poses as a Starfleet officer, and she uses a Vulcan mind meld to show Agnes Jurati visions of the Admonition, a warning about a catastrophe tied to synthetic life. Jurati is then pushed to join Picard's crew and kill the synths' creator, Bruce Maddox. Oh later leads a Romulan fleet to the synth homeworld Coppelius, but withdraws after the crisis is defused.
Oh is the chief schemer of Picard's first season. Her place at the heart of Starfleet showed how deeply the Zhat Vash had infiltrated the Federation.