Oh
Nedar, known as Oh while posing as a Starfleet officer, was a female Romulan/Vulcan hybrid flag officer in the Tal Shiar with the rank of general, loyal to the Zhat Vash, and part of the Conclave of Eight. 

She became integrated into Starfleet as a , where she worked her way up through the ranks to eventually become a commodore, and served as the director of Starfleet Security from at least 2390 to 2399.

History
Oh infiltrated Starfleet in the mid-24th century, after Doctor Noonian Soong began creating androids that matched or surpassed Human capabilities.

In 2385, Oh presided over a Zhat Vash initiation ceremony on Aia, of which Narissa and Ramdha were the only survivors. She was one of the architects of the the devastating Attack on Mars the same year. ()

In 2390, Oh issued a black flag directive to Captain Alonzo Vandermeer of the , ordering him to kill Ambassador Beautiful Flower and his protégé Jana, or risk the destruction of his ship. ()

In 2399, Jean-Luc Picard was only aware that Oh was the Vulcan chief of Starfleet security, having never met her personally. ()

Oh ran covert operations involving Romulan operatives  and her brother Narek, among others, aimed at obtaining information about the whereabouts of androids similar to Dahj and Soji Asha. According to Rizzo, she had profound reservations. At least one of these operations was inside the Federation on Earth. ()

After that operation resulted in the death of Dahj and Picard becoming aware of the androids, she went to see Dr. Agnes Jurati at the Daystrom Institute in Okinawa to discuss the doctor's meetings with Picard. () There, Oh initiated a mind meld with Jurati showing her conflated visions and images related to the supposed threat of artificial lifeforms that Oh herself experienced during her exposure to the Admonition on Aia (), before convincing Jurati to swallow a bio-organic tracking compound called viridium. ()

Oh kept a keepsake box on her desk that had the IDIC symbol displayed on the side, and a set of Vulcan bells in a shelving unit elsewhere in her office. ()

Abandoning her Starfleet cover, Oh led a Tal Shiar  squadron to Coppelius to destroy the synths living there, but encountered orchids and, eventually, a fleet of Starfleet  starships led by the . Initially unswayed by Acting Captain William T. Riker's demand to retreat because she felt her goal to defeat the Destroyer was more important than her own survival, Oh eventually fled when Soji destroyed the beacon, proving that she was not the prophesied Destroyer. ()

Memorable quotes
"Picard again? And we all thought he was safely mothballed on that vineyard of his. All these years. The Hermit of La Barre. Now suddenly he is inescapable."
"That's one word for what he is." 
-Oh and Kristen Clancy, on Picard's return ()

"Admiral Clancy, I know I need hardly remind you if the Romulans were running clandestine operations on Earth, I would know. And then you would know. And then all of Starfleet would know, because clearly, that would be an overt and intolerable act of war."
-Oh, to Kirsten Clancy, on Romulan anti-synth ops on Earth ()

"Do not insult me, lieutenant; it would not be advantageous for your career."
- Oh, to Rizzo/Narissa ()

Appendices

Appearances

Background information
Oh was portrayed by Tamlyn Tomita. An alternate name, "Nedar", was given by closed captioning in the season 1 finale, , but was not spoken on screen. "Nedar" was stated by Michael Chabon to be her real name, and "Oh" was her "sleeper agent name." 

She is the first commodore to be seen in the 24th century.

On the observation that Oh is not a Vulcan name, Chabon revealed on his Instagram page that Oh's name has a "curious relation to the Vulcan word for eight (ohkuh)".  See also: Conclave of Eight.

In "The End is the Beginning", Oh is shown wearing sunglasses. This was specified in the script as a homage to Danish-French actress .  It was previously established by T'Pol in  that Vulcans don't need eye protection due to the existence of an inner eyelid.

On that account, Michael Chabon said the following on  comment section: "Let me try to be clearer: Oh has read Jurati's psychological profile, and something in it, a tendency in Jurati's relationship to authority figures, has led her to prepare both her manner and her appearance very carefully [….] This is behavior that cops, soldiers, and teenagers, among others, engage in all the time."

Regarding Oh's background, Chabon stated that her parents (a Romulan mother and a Vulcan father) were (pretended) members of the movement which supported a Romulan-Vulcan reunification. 

A line in  firmly established Oh as being the first featured onscreen individual of Vulcan/Romulan descent. The script of  had already included an introductory note that Saavik was intended to have also been of similar descent, (; ) but the reference did not make it onscreen ultimately. A Scene 5 line establishing the fact was actually filmed, but was trimmed from the scene as eventually featured in the released film, and had not been included – neither as a reinserted scene nor as a "deleted scene" special feature – in the later-released "Director's Edition/Cut" home video formats either. The line was actually included, though, in an early contemporary promotional short, aired on television.  This was also mentioned in the ization of  .

External link

Hybrids
Romulans
Vulcans
Starfleet personnel (24th century)
Starfleet operations personnel
Starfleet flag officers
Tal Shiar personnel