The Cylons are a cybernetic civilization at war with the Twelve Colonies of humanity in the Battlestar Galactica science fiction franchise, in the original 1978 & 1980 series, as well as the 2003 reimagining. In the 1978 series, the Cylons are also the race who created the robot Cylons.
The nature and origins of Cylons differ greatly between the two Galacticas. However both series feature Cylon Raiders, Cylon Basestars and Cylon Centurions.
Original continuity Edit
The Cylons of the 1978/1980 series are not the mechanical foils seen throughout the series, but an advanced reptilian race who created the robots (who were referred to as Cylons within the show) to serve them, maintain their vast empire and to man their military forces in the face of a sudden population drop that eventually led to the Cylons' extinction - seemingly overnight. This fact is briefly mentioned in the 1978 movie-length premier of the series (near the end of episode 2 in syndication) when Apollo relates the Cylons' origin to Boxey. In the episode "War of the Gods", during Count Iblis's private discourse with Count Baltar, Baltar mentions that he recognizes Iblis's voice, referring to Patrick McNee's voicing of the Imperious Leader in the opening episode/theatrical movie (McNee also played Iblis), with Iblis countering that if that was true it must have been "transcribed" over a thousand yahren (years) ago and programmed into the mechanical body of the Imperious Leader.
The follow-up series Galactica 1980 had a two-episode arc entitled “The Night the Cylons Landed” that featured a humanoid Cylon, though unlike its successors in the post-millennial reimagining, it was not organic, but a complex mechanical construct.
Reimagined continuity Edit
The Cylons of the 2003 miniseries and current Battlestar Galactica series are fundamentally different from the Cylons of the original 1978/1980 series. In the new version, the Cylons were created by humans as robotic workers and soldiers. In the original series the Cylons almost destroy the entire human civilization, chasing a few ship-borne survivors into deep space. Unlike the original series, however, the reimagined series includes twelve Cylon models who are nearly indistinguishable from human beings. Although these human-form Cylons are the focus of the series, alongside the humanoid models there are also Centurions similar to those in the original series. Much of the Cylons' technology is based heavily on bioengineering and/or synthetic biology rather than conventional robotics. Humans often derisively refer to Cylons as "toasters", due to the resemblance of Cylon centurions to "walking chrome toasters", as described by Gaius Baltar in the miniseries.
In contrast to the largely unexplained reason for the original Cylons' genocidal mission, religion is the primary motivation of the Cylon race in the re-imagined series. They consider humans to be sinful and flawed creations of God that therefore do not "deserve" to survive. The Cylons' monotheistic faith and their descriptions of God indicate a strong similarity to the Abrahamic religions.