Special Weapons Dalek (Remembrance of the Daleks)

A Special Weapons Dalek, referred to as the Abomination was commissioned by Davros and given a travel unit that was flawed; when the Dalek first fired, the radiation from the backwash saturated its body, mutating it further. Eventually given a travel machine with an enormous gun, the Special Weapons Dalek went on to become a frontline weapon - it fought against the Thals and the Movellans as part of Davros' plan to wipe out two of the Daleks' enemies and to get revenge for past defeats.

Due to the Daleks racial purity, the other Daleks saw the Special Weapons Dalek as an abomination, hence it's name because each time the Dalek fired its gun, more radiation would saturate its cells. The Dalek was also insane because the radiation had altered its mind. It had a sense of self which made the other Daleks afraid of it.

Davros' will was the only thing that kept the others from killing it, but the Special Weapons Dalek seemed to enjoy the fear and hatred it received from its fellows. (PROSE: Remembrance of the Daleks)

It was employed by the Imperial Daleks against the Renegade Daleks to obtain the Hand of Omega during the Shoreditch Incident. After it had done its work, it returned to the Imperial Dalek mothership via the Imperial Dalek Shuttle and was presumably destroyed when the Hand of Omega destroyed the mothership. (TV: Remembrance of the Daleks)