Fifth Doctor Dalek duplicate (Dalek Soul)

The Dalek duplicate of the Fifth Doctor was created on the planet Mojox based on DNA samples acquired by the Daleks after they briefly captured the Doctor and Nyssa. While the two were able to escape captivity shortly after they reached the planet, the Doctor departed without realizing the scale of the Daleks' plans for the planet.

The Daleks created this duplicate of the Doctor with the intention of using his reputation against the rebel forces. By presenting himself as an enemy of the Daleks, the duplicate Doctor was able to infiltrate the rebels and convince them to follow battle plans that would lead them into traps set by the Daleks, limiting the rebels' ability to oppose the Daleks until they were finally defeated.

The Daleks' efforts were finally defeated when the rebel leader was able to make contact with the Dalek duplicate of Nyssa and convince her of her true nature. Nyssa subsequently sabotaged her viral research so that the final result was a virus that would drive the Daleks to destroy themselves rather than the Mojoxalli, which also destroyed herself and the duplicate Doctor (AUDIO: Dalek Soul).

Personality
Unlike his template, the duplicate Doctor was cruel and sadistic, taking great pleasure in witnessing the rebels' plans fail due to his own sabotage. He was also completely loyal to the Daleks, considering their 'inevitable' victory natural. The Nyssa duplicate, after witnessing video footage of the original Doctor, mused that the duplicate had been allowed to keep some aspects of the original's ingenuity and personality, but had been completely stripped of his moral centre to make it easy for the Daleks to use him as their agent (AUDIO: Dalek Soul).