Sera was the identity assumed by a female Romulan surgically altered to appear Human. She was an operative who had been sent through time, from the future to 20th century Earth, on a mission to impede Human progress. She planned her actions based on computer simulations, and did not personally understand how exactly they would lead to the desired effects on the timeline.
Originally, Sera sought to assassinate Khan Noonien Singh in 1992, which would have averted the Eugenics Wars and the formation of the United Federation of Planets. However, due to Khan's ascendance being the target of multiple temporal incursion attempts from factions in the Temporal Wars, she found herself unexpectedly trapped on Earth for thirty years waiting for Khan to appear.
In 2022, Sera destroyed the Lake Ontario Bridge in Toronto with photonic bombs, so as to sow international strife. In the aftermath, she noticed La'an Noonien-Singh and an alternate timeline version of James T. Kirk pursuing a van carrying a piece of debris from the bridge. Realizing that they must have come from the future as well, she decided to manipulate them to her own ends.
After extricating Noonien-Singh and Kirk from the Toronto City Police, Sera pretended to be a conspiracy theorist and fed them clues about an impending Romulan attack on a secret cold fusion reactor in Toronto – in actuality her own objective. Noonien-Singh and Kirk proceeded to locate the reactor within the Noonien-Singh Institute for Cultural Advancement, whereupon Sera revealed herself and held them at gunpoint. When Kirk refused to cooperate, Sera fatally shot him and forced her way into the NSI with Noonien-Singh.
With security guards closing in and the reactor no longer accessible, Sera changed her goal to killing the child Khan, who was also being studied in the NSI facility. Outside Khan's room, Noonien-Singh managed to disarm her and shoot her with her own weapon. As she lay dying, Sera activated a hidden device on her neck that disintegrated her body.
In Kirk's alternate timeline, Sera successfully destroyed the cold fusion reactor, which wiped out Toronto and triggered a war between Humans and Romulans that devastated Earth and prevented the founding of the Federation. (SNW: "Tomorrow and Tomorrow and Tomorrow")
Sera was played by Adelaide Kane.