The Dalek Emperor made its debut in episode 6 of the Season 4 story ‘The Evil Of The Daleks‘ and was the supreme ruler of the Dalek Empire, commanding the Dalek race and the planet Skaro.
The Emperor remained in an enormous, immobile, conical shell plugged into a corner of the control room in the Dalek City on Skaro. It was connected to the wall by tubes, and spoke in an echoing voice.
This Emperor tried to blackmail the Second Doctor. He ordered the Daleks to capture the Doctor so that they could force him to conduct research into the Human Factor. This would unlock the secrets of the Dalek Factor which was to be spread throughout all areas of human history, giving all humans the mentality of a Dalek and preventing the Great War from ever happening. He was seemingly destroyed by a civil war between humanised Daleks and un-altered Daleks. However, a light was seen blinking on its casing at the end, indicating some kind of activity.
Watch the reveal of the Emperor Dalek in this reconstruction of the lost scene from ‘The Evil Of The Daleks‘ on the ASpaceHelmet ForACow YouTube Channel.