Emperor Type 1

Despite not being a Dalek himself, (TV: Resurrection of the Daleks) Davros, the Kaled scientist responsible for the creation of the Daleks, was housed in a distinct Dalek casing during his time as leader of the Imperial Daleks, designated the Emperor Dalek. (COMIC: Emperor of the Daleks!, TV: Remembrance of the Daleks)

Characteristics
As Emperor Dalek during the Civil War, Davros' operated a casing coloured mostly white with gold livery, matching the Imperial Daleks he commanded. The casing was composed of a lower travel unit with gold sense globes, which appeared identical to those of the Imperial Dalek drones. However, what distinguished the casing was its top half; rather than a standard dome atop the upper grating section and middle section, Davros' body was housed within a large, spherical dome similar to earlier Emperors, such as Davros' immediate predecessor and the Golden Emperor. Unlike his predecessors, Davros' casing completely lacked the middle weapons platform and so sported no manipulator arm or gunstick. The dome itself was adorned with a pair of Imperial Dalek luminosity dischargers, however, it lacked the standard Dalek eyepiece; in its place was an energy relay which appeared as a silver hexagon with black outlines. A split between the hemispheres enabled Davros' to open up the dome, thus exposing himself, at will. (TV: Remembrance of the Daleks)

Following the Shoreditch Incident, Davros began to modify his casing; in a reflection of his mind's downward spiral into thinking of himself as simply "the Dalek Emperor", he introduced elements reminiscent (AUDIO: Terror Firma) of the static, tower-like casing used by the original Dalek Emperor in the Dalek City at the time of the original Dalek Civil War. (TV: The Evil of the Daleks) During the Emperor formerly known as Davros's encounter with the Seventh Doctor, the transformation was complete, with a standard eyestalk, manipulator arm and gunstick having been added to the casing, making it almost identical (COMIC: Nemesis of the Daleks) to the casing used by the Golden Emperor on the eve of Davros's takeover. (COMIC: Emperor of the Daleks!)

A day to come
While dormant following his own Daleks' attempt to exterminate him, Davros, the Daleks' own creator, (TV: Genesis of the Daleks) began to reflect that the Daleks would need him as "their Emperor" to reach their full potential and destroy "all opposition". (WC: Risen) After awakening and meeting Daleks in the flesh shortly thereafter, however, it was the title of Supreme Commander which he claimed. (TV: Destiny of the Daleks)

On Necros, the Sixth Doctor suggested that Davros intended to become Emperor of the new race of Daleks that he created in opposition to those who followed the Supreme Dalek (TV: Revelation of the Daleks) and its master, the Dalek Prime. (COMIC: Emperor of the Daleks!, PROSE: War of the Daleks)

Davros the Emperor
According to one account, shortly before the outbreak of the Imperial-Renegade Dalek Civil War, the Dalek Empire's Emperor had disappeared. In his absence, the Dalek Supreme intended to crown himself as the new Emperor, and had an Imperial Casing created. He intended to crown himself at the conclusion of Davros' trial. However, during the trial, Davros managed to win over the Daleks to his side; while the Dalek Supreme was forced into hiding, building a new faction of Daleks to stand against the now Davros-loyal Empire, Davros was transferred to the ready-made Imperial Casing to mark his ascendance to the throne. (AUDIO: The Davros Mission)

According to another account, after having escaped Dalek custody at his trial, Davros returned to Skaro from Spiridon, and successfully usurped control of the Dalek Empire from the Golden Emperor, only to be gravely wounded by Abslom Daak, who used his chainsword to cut Davros' life-support chair in half. Following this, what remained of Davros' body was salvaged by his loyal Imperial Daleks, who housed him within a specially made casing as he was named the new Emperor Dalek. (COMIC: Emperor of the Daleks!)

It was from within the casing of the Emperor Dalek that Davros led the Daleks from the Imperial Dalek mothership during the Shoreditch Incident. Contacted by the Seventh Doctor, Davros opened up his dome to reveal himself in their televisual meeting. Soon after, Davros was forced to use an escape pod to evacute the mothership, which was destroyed by the Hand of Omega. (TV: Remembrance of the Daleks)

By the time of his confrontation with the Eighth Doctor, Davros' casing was modified. He himself teetered on the edge of sanity, his mind split between two warring personalities — Davros and "the Emperor", with the latter ultimately prevailing. (AUDIO: Terror Firma) The Seventh Doctor met a Dalek Emperor whose casing was even further along to looking like an ordinary Dalek casing, now possessing an eyestalk; in fact, this made him appear almost identical (COMIC: Nemesis of the Daleks) to the Golden Emperor, Davros's own opponent, as he had appeared just prior to the oubtreak of the Imperial-Renegade Dalek Civil War. (COMIC: Emperor of the Daleks!) Asking the "Emperor" about Davros, the Doctor found that he didn't even have any memory of the name, and the Doctor was briefly saddened when he realised what had happened. (COMIC: Nemesis of the Daleks)

However, Davros ultimately reemerged, back to his original personality, and remained an asset to the Daleks during the "very first years" of the Last Great Time War, with his chair being reconstructed. (TV: The Stolen Earth)

Behind the scenes
The Discontinuity Guide suggests that, whilst undergoing interrogation during his incursion into Dalek history, the Fourth Doctor had told Davros of the Human Factor Incident, which involved a Dalek Emperor, and so influenced the Dalek creator to later name himself Emperor of the Imperial Daleks.