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This article covers the various depictions of Lucifer from the tie-in novelizations, comic books, and other media.
Unlike his canonical analogue, Lucifer is not a Cylon but an ambulatory cybernetic sentience that the Cylons created as a result of their developments into war machines, presumably during the Thousand Yahren War. However, unbeknownst to his Cylon masters, he believes he has a soul, since he "created" his own personality. Additionally, he is able to override much of the Cylons' programming, with the exception of the extreme loyalty that is deeply embedded into his programming.
Despite not being a Cylon, Lucifer is afforded both an official name and a secret name; his official name, Lucifer, is an acronym for his secret name. He is also able to create various machines, some of which were used in Baltar's training.
Lucifer rescues Baltar from execution, forcing the human to undergo diet, as well as mental and physical exercises, for the purposes of Lucifer's plan to use Baltar to destroy Adama's Fleet. After Lucifer's plan and Baltar are presented to the Imperious Leader, Baltar is able to have Lucifer reprogrammed to be totally subservient to him.
Although Lucifer is able to negate the program's effects, Lucifer ends up acquiescing to it and saves Baltar from death on Kobol. However, his exposure to Lieutenant Starbuck—previously captured by a Cylon patrol before encountering Kobol—leads him to think favorably of certain humans. Starbuck introduces Lucifer to pyramid and beats him at the game. Lucifer is baffled by the concept of luck as Starbuck describes it.
Lucifer is dismayed by Spectre's flattery of Baltar, despite Lucifer's attempts to convince him of Spectre's duplicitous nature. He is beside himself when Spectre not only manages to fool Baltar into authorizing his retreat from Antila, but also Baltar's assignment of Spectre as Lucifer's aide. It is also revealed that Lucifer has created a system that he believes will enable him to beat Starbuck at Pyramid should they ever have the opportunity to play it again.
Lucifer and Spectre are taken captive by smugglers and are taken to a planet where Lucifer winds up meeting Starbuck after he is also taken prisonser. Starbuck eventually convinces their captors to allow him to play Lucifer at Pyramid for a chance at freedom. But the terms are that if Lucifer loses, he will be deactivated. At the end of the game, Lucifer simply lays his cards face down and congratulates Starbuck. Later, after the aliens are defeated, Lucifer willingly deactivates himself despite Starbuck's protests. Spectre takes the deactivated Lucifer back with him. Spectre examines Lucifer's cards and discovers that Lucifer had a winning hand.
Spectre is made Cylon commander and has Lucifer reactivated, reprogramming him to be a saboteur. Lucifer is then sent to infiltrate the Galactica fleet disguised as a Borellian Nomen. He eventually attempts to murder Adama but is thwarted by Starbuck, restoring his memory in the process. Later, Lucifer decides to join the Colonials.
Some 30 years after the events of "The Hand of God," Baltar returns to the Cylons and, with Lucifer, executes a plan whereby they silently pursue the Fleet until they locate Earth. This plan is successful (Galactica 1980 2) and they begin their attack on Earth. In the final battle, Lucifer meets his end when his Cylon basestar is destroyed. (Galactica 1980 3—4).
Lucifer lands on Kobol and discovers Baltar still alive. Baltar pleads with Lucifer, saying that he can lead the Cylons to the Fleet, a claim that Lucifer sinisterly agrees with (The Memory Machine). Lucifer later leads an attack on Galactica and the Fleet near the scavanger world, in the middle of the magnetic void, without success (The Trap!, Collision Course!).