Battlestar Galactica's 15 Biggest Plot Twists And Reveals

Battlestar Galactica had always made an event out of the revelation of a new Cylon. By the time we got to the mid-point of the final season, they were all known, but one. And in an episode that is filled with many devastating moments, Sometimes a Great Notion saves its biggest reveal for its final scene: the last Cylon is Ellen Tigh.

Ellen was a complex character—sometimes sympathetic, sometimes deplorable, and at times both devoted and faithless to her husband Saul. By the time her nature is revealed, Ellen had actually been dead for well over a season, executed with as much mercy as possible by her own husband for betraying the human resistance. So the discovery that she was actually a hidden Cylon is not what anyone was expecting.

It is only four episodes later that Ellen is shown to still be alive, having resurrected on the Cylon fleet after her death. From then on, she becomes one of the series’ most significant characters, helping to provide a lot of understanding about the backstory for the entire human-Cylon conflict.