"I'm nothing like her, Michael. She's terrifying, she's… she's like a twisted version of everything I've ever aspired to be. I'm gonna have nightmares about myself now."
Captain Sylvia Tilly was a female Terran Imperial Starfleet officer who lived during the mid-23rd century.
By late 2256, she was the captain of the ISS Discovery. She had assumed command by killing the ship's previous captain, who had been recovering from the Crestian flu.
Prior to Discovery, she had been at the Imperial Starfleet Academy. Among the locations where which she distinguished herself during her career were Quam, Elpha, and Purmata VI. She was also known as "The Slayer of Sorna Prime," "The Witch of Wurna Minor," and "Captain Killy." (DIS: "Despite Yourself")
Working closely with Emperor Georgiou, who claimed they had great fun together, they subjugated the Betazoids and "wiped out" Mintaka III. (DIS: "Will You Take My Hand?")
During her career, she won the Valor, Master of Poisons, and 50 Kills medals. (DIS: "Despite Yourself")
The image of Tilly was portrayed by Mary Wiseman.
It is likely she was killed when the Discovery was destroyed in the prime universe, although this has not been confirmed.
The mirror Tilly and the ISS Discovery are expected to appear in Star Trek Online as part of the anniversary event in early 2019.