Captain Sylvia Tilly (also known as "Captain Killy") is a Terran Captain and the Mirror Universe counterpart of Cadet Sylvia Tilly. In 2256, Tilly was in command of the I.S.S. Discovery. When the U.S.S. Discovery jumped into the Mirror universe using the spore hub drive, Tilly, her ship and her crew were thrown into the 25th century of the Prime universe where she remains at large.
Similar to her Prime universe counterpart, Sylvia Tilly was aboard a Malachowski-class vessel during a training cruise when the ship's captain was killed. Tilly took the opportunity of the created vacuum in leadership to seize command of the ship. She also killed the ship's First Officer (a Mirror universe counterpart of the player). According to other Terran captains such as Evelyn Savea, Tilly murdered the First Officer with a spoon. ( “Pahvo Dissension”) According to Tilly herself, the death was swift and painless. ( “Para Pacem”) However, it is revealed that Tilly, claiming to have killed the player’s mirror self, was lying as they appear onboard the I.S.S. Reskava in 2411. ( “Firewall”)
Some time later, she would take command of the I.S.S. Discovery while the previous captain was in bed with the flu. (Despite Yourself) In her career, she participated in attacks on Betazed and Mintaka III with Emperor Georgiou. Her reputation earned her various nicknames, including "The Slayer of Sorna Prime," "The Witch of Wurna Minor," and "Captain Killy." (Will You Take My Hand?, Despite Yourself)
In 2256 the I.S.S. Discovery was ordered to Pahvo, which was considered a de facto death sentence due to the deadly nature of the planet. Before she could be attacked by Pahvo, she came under attack from a large Klingon fleet. During the battle, the U.S.S. Discovery jumped to the Mirror universe, switching places with the I.S.S. Discovery. I.S.S. Discovery, as well as the rest of the Klingon fleet, ended up in the Prime universe at Pahvo in 2410. ( “Para Pacem”, The War Without, The War Within)
Upon their arrival, an Alliance vessel was present in orbit of the planet. Tilly enlisted ship's aid by claiming asylum and used them to fight off the Klingon attackers as well as her own mutineers who objected to seeking aid from the Alliance. During the ensuing battle with Klingon forces, Tilly beamed down to Pahvo and managed to manipulate it with agonizer technology into aiding her. Having turned the planet into a weapon under her control she destroyed the Klingon attackers and damaged the Alliance ship, giving them a warning to stay away and stating her intent to use Pahvo to create a new empire under her control. ( “Para Pacem”)
The Alliance vessel eventually returned to the planet and its crew managed to disable the agonizer technology. However, Tilly managed to escape using the planet's transmitter as a long range transporter. Her crew, having been abandoned by her, agreed to return to the 23rd century where they would eventually be destroyed by Klingon forces. The remnants of the I.S.S. Discovery would be mistaken by Starfleet as wreckage of the U.S.S. Discovery. ( “Illusion of Communication”, The War Without, The War Within)
- “Para Pacem”: Tilly's Discovery appears in 2410, under attack from Klingon forces also thrown forward in time. She requests asylum from the Alliance.
- “Illusion of Communication”: The player must counter Tilly's plan to weaponize Pahvo's transmitter.
- “Pahvo Dissension”: She is mentioned in the lore and Terran Captain will sometimes mention her in the slurs addressed to the players.
- The Ten Forward stream coinciding with the launch of Season Twenty-four: Reflections has the developers confirming that Mirror Tilly, having claimed to have killed the player's mirror self, was lying as they appear in the ending cutscene of “Firewall”. (Ten Forward Weekly: Operation Wolf (15 September, 2021)
- Sylvia Tilly (mirror) at Memory Alpha, the Star Trek Wiki.
- Sylvia Tilly (mirror) at Memory Beta, the non-canon Star Trek Wiki.