Lucifer

Lucifer sits on the throne in Baltar's absence.

The Cylon IL-series attached to Baltar, who was assigned to seek out Galactica's Fleet and destroy them. He initially presumed that he would learn much from the Human who betrayed his own race. (Saga of a Star World)

Lucifer had clear and present distrust of Specter, and attempted to convince Baltar of the problems Specter had. (The Young Lords)

Voiced by Jonathan Harris

Animated by Felix Silla

Notes

Lucifer is named after the fallen angel depicted in texts of Roman Catholic and other origins, also another name for the Devil.

Maybe all IL-series Cylons are named after some form of demon in homage to Count Iblis, who originally had control over the Cylons. Though this is just speculation

Lucifer's "first" appearance was in the final scenes of "Saga of a Star World", in which Baltar was spared execution by the succeeding Imperious Leader, Barkol.