Cally was a strong-willed, rebellious member of the Auronar.
History
Like all Auronar, she was born of the cloning process and was in the same sibling group as Zelda. She was rebellious, and was determined to oppose the Terran Federation's dominance over the rest of the Milky Way. Because of this, Cally was exiled from Auron.
She eventually reached Saurian Major, joining the rebels there. When the rebel group was eventually wiped out, Cally was the last survivor. She prepared to assault the communication relay station on the Saurian Major in a guerrilla suicide mission. Roj Blake arrived on the planet and interrupted her effort -- convincing her to join him aboard the Liberator.
Shortly after joining the crew, Cally's inherent psychic abilities were hijacked by the Lost. Through their influence, Cally sabotaged the ship and steered it into a trap, which could only be escaped if Blake helped the Lost to destroy the Decimas they had created. Ultimately, the crew of the Liberator managed to escape and the Lost were destroyed by their own creations. Despite these events, the majority of the crew -- with the notable exception of Jenna Stannis -- quickly came to trust Cally, particularly for her strategic knowledge and medical ability. She also earned her keep through use of her considerable mechanical and engineering skills. Kerr Avon had a sincere affection for Cally, though he found her idealism and compassion to be only slightly less irksome than Blake's.
This trust proved vital, as Space Commander Travis soon captured Cally and held her as bait for Blake. The trap was defeated, and Cally returned to the crew.
Some time later, Cally's psychic gifts proved to be a liability when an entity from another dimension attempted to take over her mind. With the aid of Orac and moon discs, Cally was able to defeat the entity and banish it from the Prime Reality altogether.
When the rest of the crew, save Avon and Cally, were captured on the planet Horizon, Cally single-handedly went to the planet's surface to rescue them -- much to Avon's chagrin. She also was the first to detect the virus aboard the Wander K7 -- though the warning was not enough to prevent the virus from being unleashed upon the Q-Base on Fosforon.
Shortly before the beginning of the Intergalactic War, Cally questioned Blake on the fanaticism he displayed in wanting to destroy Star One. Her fears were justified, in that Blake's decisions ultimately placed the Liberator in the crosshairs of the Andromedans at the onset of the war. As such, the entire crew was forced to flee the ship while it made repairs. Cally ends up in the hands of the Chengans, destined to be killed for organ harvesting alongside Vila Restal, but both of them were teleported back aboard the Liberator in time to save their lives.
After Orac sabotaged the ship, Cally found herself face to face with the Thaarn, a legend of her homeworld. Though the Thaarn offered to share the entire universe with Cally, she opted instead to trick him and freeing her captive crewmates.
Cally's activities with the renegade Blake's 7 ultimately put the Auronar at risk. Enraged, Servalan set Auron in her sights. Determined to use their technology to make a clone of herself, and also to lure the Liberator into a trap, Servalan unleashed a deadly plague on the planet. Cally, across light years, heard the psychic distress call from her sister Zelda and urges her crewmates to respond. They do so, but are unable to completely stop Servalan's plot. They manage to escape Auron with a number of survivors, relocating the remainders of the Auron people. Although Cally was griefstricken, she remained with the crew.
After this, an undead alien's psychic manifestation possessed Cally and took control of the Liberator. With the threat facing the entire crew, Avon drew upon Cally's deep-seated loyalty for her compatriots and helped her to psychically overpower the undead creature.
Cally ultimately met her end on the planet Terminal, caught in an explosive trap laid by Servalan.
Source
Cally is derived from Blake's 7.