Not quite. The Beings of Light (if you’re referring to TOS lore) were supposed to be the original ascended Lords of Kobol, from which the Colonial Humans descended.
Iblis was cast out from them, and twisted up into a kind of demonic entity, or possibly the last member of another ascended species entirely that were enemies of the Seraphs - nobody really knows. He was the one who created the first Imperious Leader with three brains, the third of which was said to have been built by Iblis himself, containing a part of his essence to control the Cylons through the Leader (hence the intentional use of Patrick Macnee’s voice throughout the show and Baltar recognizing him as such on the Prison Barge). The original reptilian Cylons embraced the cybernetic technology that Iblis provided until it took them over almost completely.
In the original concept, there were still biological Cylon bits inside the robots containing single brains (and 2 brains in gold-plated Commanders like Vulpa and IL-series Cylons like Lucifer and Spectre), making them technically cyborgs, but TV “sensibilities” at the time weren’t compatible with our Colonial heroes blowing away other living beings every week, so they changed the nature of the Cylons to be purely mechanical robots who deposed their original reptilian masters after Iblis’ influence fully took over.
Update:
For those wondering, this was the original Larson concept of the Cylons. The first image was from the introduction of a repackaged TV movie that put together bits of multiple episodes, showing the early history of the Colonial-Cylon war:
Then later, Realm Press comics did a storyline of the original Cylons coming back to help the Colonials fight their creations:
From these, I built some orthos of what the full body might look like:
View attachment 11371
View attachment 11372
Honestly, they kind of look like giant humanoid snapping turtles to me.
