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 and 1980 series, the 2004 reimagining, as well as the spin-off prequel series, Caprica. In the 1978 series, the Cylons is also the name of the race who created the robot Cylons.
The nature and origins of Cylons differ greatly between the two Galacticas. However both series feature Cylon Raider, Cylon Basestar and Cylon Centurions. The prequel series, Caprica, focuses on the creation of the Cylons, which differs from all the previous Battlestar Galactica series.
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 premiere 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 Macnee's voicing of the Imperious Leader in the opening episode/theatrical movie (Macnee 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.
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