Lt. Sharon "Boomer" Valerii was a Humanoid Cylon of the "Number Eight" line, who was assigned to infiltrate the Colonial Feet as a sleeper agent. For two years she served as a Raptor pilot on Galactica, where she developed a sexual relationship with fellow Humanoid Cylon Galen Tyrol, neither being aware of their true heritage. Following the Fall of the Twelve Colonies and Galactica's unexpected escape, Valerii began drifting back and forth between her human and Cylon personas committing acts of sabotage on behalf of a Number One taking the guise of a priest. After an attempted assassination attempt on Commander William Adama, she was murdered by a crewmember and returned to the Cylon fleet. For the next eight months, Valerii worked with Caprica Six to start a revolution in opposition to the genocide. This ultimately led to the Cylon occupation of New Caprica, principally to provide reparations but with other Cylons gradually turning towards continued genocide. When the colony failed in an uprising, Valerii was taken under the priest Number One's wing as his protege. This led to the Cylon Civil War, when the Twos, Sixes and Eights saw Valerii voting against her fellow Eights as an attack on their democratic system masterminded by the Ones, with the rebels destroying the Resurrection Hub before taking refuge in the human refugee fleet. Valerii feigned disgust in a plot to deliver the Cylon Ellen Tigh to Galactica and abduct Sharon Agathon's human-Cylon hybrid, Hera. At the Colony, Valerii had an honest change of faith at the realisation Hera was to be killed and mutilated to satisfy their curiosity. Though she returned Hera to her mother, she was killed and, without resurrection, was gone forever.

Life on Caprica and GalacticaEdit

Lieutenant Junior Grade Sharon "Boomer" Valerii is a Cylon sleeper agent programmed to believe she is human. For example, she has been implanted with false memories of being raised on Troy by her parents Katherine and Abraham Valerii, who supposedly died in an accident killing all the members on the mining colony. Whether or not Katherine and Abraham actually existed is unknown. In the time before the mini-series, Boomer and Galen Tyrol are romantically involved, although their relationship is against military protocol (she is an officer, he's enlisted). Due to her programming, she performs a number of sabotage actions (including bombing the Galactica's water tanks) but has no conscious memory of these actions. Tyrol trusts her and hides evidence implicating her in the water bombing but later suspicious events cause him to break off his relationship with her. In time, she begins to suspect something may be wrong with her. She asks Gaius Baltar to administer a blood test to determine whether she is a Cylon. Although his test demonstrates she is in fact a Cylon, he decides to not inform anyone out of fear she will kill him. She is relieved for a while but gradually her suspicions return and she attempts suicide. Her programming, however, prevents her from killing herself.

In the episode "Kobol's Last Gleaming", Commander Adama sends Boomer on a mission to destroy the basestar orbiting Kobol. On the basestar, she encounters numerous other Number Eight copies identical to herself but she refuses to accept she is a Cylon and personally sets the bomb. After returning to Galactica, her hidden programming takes over and she shoots Commander Adama twice in the chest, putting him in a coma. She is put in the brig and violently interrogated by Colonel Tigh, who has taken command of Galactica during Adama's incapacity. Tyrol is also suspected of being a Cylon because of his relationship with her, and is thrown in her cell. He tells her not to speak to him or even touch him; he insists she is a machine and nothing like him.

Death and ResurrectionEdit

Gaius Baltar forces Boomer to tell him how many other Cylons are still hidden in the fleet by injecting Tyrol with a substance that stops his heart and refusing to administer the antidote. Sharon finally tells Gaius there are eight Cylons in the fleet. She is shot and killed by Cally, who blames her for Tyrol's imprisonment; Cally herself is in love with Tyrol as is made clear in later episodes. Sharon dies in Tyrol's arms, telling him she loves him.

In the episode "Downloaded", it is revealed Boomer's consciousness has been downloaded into a new body. She tries to live on Caprica like in her old life as a human. She resists being identified with the Cylon cause, although they view her and Caprica Six as heroes. Over time, she begins to open up to Caprica Six, who like her has been transformed by their love for a human. They decide to try to persuade the Cylons some of their actions against mankind are wrong. Number Three threatens to have them "boxed", that is, placing their consciousness into "cold storage". Boomer is among the Cylons occupying New Caprica. She has accepted herself as a Cylon and is fully integrated back into their society. She functions as a member of the Cylon governing council that controls the puppet human government under President Gaius Baltar. Her desire remains to show humans and Cylons can co-exist, however, relations between the two groups turn increasingly hostile. Boomer visits Cally who has been imprisoned to tell her she is doing everything that she can to free her, and attempts to make peace. She indicates she has accepted Tyrol moving on and starting a family with Cally. However, Cally remains distrustful and angrily rebuffs her.

Relation to Hera Agathon and 2nd DeathEdit

In the episode "The Eye of Jupiter", Boomer is seen attempting to care for Athena's hybrid child Hera, who is mysteriously ill. She is frustrated by the child's deteriorating health and their inability to bond. She later joins D'Anna and Cavil when they go to meet Adama and Roslin on Galactica. Athena identifies Boomer as the Cylon who shot Adama, and Tigh informs her that her visiting privileges have been revoked. Boomer tells Athena that Hera is still alive and living among the Cylons, but has fallen ill.

Athena arrives on the Cylon Base Ship and is reunited with Hera who immediately stops crying. Caprica Six is amazed how Hera responds to being back with her "real mother", however Boomer is upset. Athena determines Hera would best be treated by a human doctor. Boomer accuses her of having planned to take Hera back to Galactica from the start. Boomer says the failure of New Caprica has taught her humans and Cylons cannot co-exist and should go their separate ways. Throughout this meeting, Boomer becomes increasingly distressed and emotionally unstable. She suggests Cavil may be right that the Cylons are not supposed to have children, and ultimately threatens to snap Hera's neck, but her own neck is snapped by Caprica Six for endangering the future of the Cylon race.

2nd Resurrection and Relation with John CavilEdit

Shortly thereafter, Boomer again resurrects. She has begun to develop a relationship with John Cavil, a Cylon who embraces his machine nature and sees human traits as a weakness. Cavil insists the Raiders should undergo a procedure to remove or at least reduce their sentience, and he enlists Boomer's aid when the Cylons become deadlocked over the matter. While her fellow Eights vote as a group against the procedure, Boomer decides to vote yes in order to make the Raiders effective fighters once again. In so doing, she becomes the first Cylon to ever vote against her own model (meaning that in a six-vote bloc, she casts an unheard-of seventh vote).

After Cavil is gunned down by Natalie's forces, he resurrects and begins to plot the permanent death of the opposing Cylons, including Boomer's fellow Eights, by killing them out of range of a Resurrection ship. Boomer has doubts about killing her "own sisters", and when Cavil reassures her the souls of the others will be looked after by God, she asks, "what about our souls?" Cavil assures her, "We're machines, machines don't have souls."

Relation to Ellen Tigh and Return to GalacticaEdit

Boomer is the only other Cylon who Cavil has told that he is keeping their creator, Ellen Tigh, prisoner. He teaches Boomer to let go of her human traits to become a better machine. Cavil describes Boomer as "self-destructive, hyper-emotional, torn apart by conflicting emotions." Boomer asks Ellen if she feels any regret for limiting the Cylon by making them as close to humans as possible. Ellen says she gave them free will, the ability to think creatively, to reach out to others with compassion and love. Boomer asks angrily who she should love.

When the Resurrection Hub is destroyed, Cavil and Boomer demand Ellen help them redevelop the technology. Cavil threatens to cut open Ellen's brain in order to access her knowledge, but Boomer spirits her away in a Raptor, telling Ellen she is forgiving her. When they arrive on Galactica, Tyrol identifies her as Boomer and she is immediately taken to the brig.

"Did Boomer really love the Chief? That’s an interesting question and one I don’t have a neat answer to. Boomer is deeply conflicted. I think the process of having false memories planted in her, getting switched “on” as a Cylon, shooting Adama, getting shot by Cally, and her experiences on New Caprica have left her severely disturbed. She was determined to go through with her mission, but in the process of seducing Tyrol she reawakened feelings of love that she thought were dead. I think she experienced real misgivings just before she got on that Raptor, but felt she had gone too far to back down. Wrapped up in that is her perverse envy of Athena, who obtained everything Boomer once wanted, and this festered into a sick desire to strike out at Athena. It’s difficult to say someone who did that loves the Chief, and yet in her damaged way, I think she did and still does love him."
Writer David Weddle discussing the character of Boomer.

The Cylon rebels decide to put her on trial for treason, with capital punishment possible due to the loss of resurrection. When Tyrol goes to see her in the brig, she professes her continued love for him. She shares with him projections of their dream home on Picon, in which they are married and have a daughter. Convinced she will be found guilty and executed, Tyrol helps her escape.

Relation of Hera AgathonEdit

She beats Sharon "Athena" Agathon and hides her, bound and gagged, in a bathroom stall. She puts on a pilot uniform and starts cleaning up, however, Karl Agathon finds her before she can leave. Thinking she is his wife Athena who is set to go on a six day mission, he starts seducing her. Boomer tries to leave but then changes her mind and has sex with him. She then picks up Hera from the daycare center and quickly drugs her with a drink. Boomer hides Hera in a provisions supply case to be loaded onto a Raptor. She assures Tyrol she was not lying about what she told him.

"Boomer is much more tragic and conflicted, and in a lot of denial. Athena came from a very different starting point, and everything was a lie, but she fought and made it through the trenches. She's a story not of privilege, but about creating whoever you want to be. That's the American story. Boomer could have been a number of things too, but she made a lot of poor decisions."
Actress Grace Park discussing the characters of Boomer and Athena.

Adama has been alerted Boomer is impersonating Athena and tries to stall her. However, Boomer figures out she has been discovered, and starts powering up her Raptor. Adama warns her he will shoot her down but Boomer tells him she has Hera. Adama starts closing the flight pod but she manages to fly out, clipping her port wing. She then quickly jumps away, close enough to damage Galactica from the resulting spatial disruption. Ellen later concludes everything Boomer did, including helping her escape, was planned in order to kidnap Hera and bring her to Cavil.

Final DeathEdit

Boomer keeps jumping her stolen Raptor headed for The Colony. Hera cries for her mother and Boomer goes to sedate her but cannot bring herself to do it. Instead she tells Hera about her projection of her and Tyrol's home on Picon and Hera surprises her by revealing she can project too and joining her in the projection. Boomer shows Hera the bedroom she dreamed of for her daughter and bonds with the girl. She ultimately takes her to Cavil but has doubts when Hera calls out for her. During the Colonials' assault on The Colony to rescue Hera, Boomer is shocked that Simon continues examining Hera. When he refuses to stop, Boomer kills him and takes Hera to the rescue party and returns her to her parents. Athena does not wish to forgive Boomer, who says she knew it would likely be her last act. She says she owed something to the Admiral, who had not ejected her from the Colonial Fleet when she kept failing to make proper landings. Boomer is then shot and killed by Athena. With the loss of Resurrection, her death is final.

Dual Sleeper modeEdit

The movie Battlestar Galactica: The Plan shows that while she was a sleeper agent aboard Galactica, Boomer had a submerged personality who was aware of her true nature and had a romantic connection to the Brother Cavil aboard the ship, though she was extremely conflicted about her actions. Cavil used an elephant figurine as a trigger to switch Boomer from one mode to the other. This Boomer revealed that she had feelings for Tyrol too and cared deeply for Admiral Adama and stated that she preferred her human personality being in control, that she liked herself better when her main self was in control. This personality blew up the water tank (and came up with the plan to do so) and shot Adama, but she said to do so, she had to mentally make herself a Centurion which deeply disturbed her. After hearing this, Cavil abandoned Boomer to her fate in the brig and this personality never seemed to emerge again. The prostitute Six (and even Tyrol) believes that when she shot Adama, she purposefully didn't kill him.

Call sign originsEdit

The call signs for both Sharon characters derive from the names of characters in the original Battlestar Galactica series. Boomer was the name (not the call sign) of a Viper pilot character played by Herbert Jefferson, Jr. Sharon Agathon's call sign, Athena, in the original series was the name of Commander Adama's daughter Lieutenant Athena. Athena was the sister of Captain Apollo, with the duties of bridge officer, shuttle pilot, and occasional Viper pilot.