Dalek duplicates, also known as Dalek replicants, were genetically engineered soldiers created by the Daleks. They were conceived as copies of individuals killed by the Daleks, to be used in undercover work. Despite this, the duplicates retained some memories, leading them to fight their programming. (AUDIO: Enemy of the Daleks) According to one account, they were androids. (COMIC: The Dalek Project)
Biology
Duplicates were incredibly strong and were able to perfectly mimic voices. Among some issues with replicants were their cold skin (AUDIO: The Genocide Machine) and eye colour, which the Daleks could never get right. (AUDIO: Daleks Among Us) Duplicates emitted a magnetic field. (COMIC: The Dalek Project)
History
On Bliss, the replicants gained a reputation. (AUDIO: Enemy of the Daleks) The Supreme Dalek planned to use a duplicate of the Fifth Doctor to assassinate the High Council of Gallifrey, but he escaped before the duplicate was completed. Davros converted some of the duplicates to his own cause and they were all killed off in the crossfire between the renegade and imperial Daleks. The Supreme Dalek vowed to create more duplicates and invade Earth. (TV: Resurrection of the Daleks)
Daleks used copies of the Fifth Doctor and Nyssa to create a virus to wipe out the people of Mojox. (AUDIO: Dalek Soul)
The Daleks created duplicates of Thals for their research on Thaleks. A replicant of Tamarus was destroyed by the Thal-Daleks. Dalek Duplicate technology was crude. (AUDIO: Brotherhood of the Daleks)
In 1915 during the First World War, the Daleks on their saucer fired a missile on a plane piloted by Lord Hellcombe's son, Ralph, and used his remains to create a robotic duplicate of him to convince Lord Hellcombe that the Dalek claimed to be the last of its race had saved his son, and manipulate him for the Dalek Project. However the Eleventh Doctor has turned Ralph to his cause and he destroyed the saucer, killing himself in the process. (COMIC: The Dalek Project)
In Paris circa 1921, the Dalek Time Controller created a duplicate named Adelaine Dutemps from its own DNA. She was ultimately mutated and transformed into a Dalek herself. (AUDIO: The Monster of Montmartre)
Upon being brought aboard the Combined Galactic Resistance command ship, Aristotle, the Twelfth Doctor and Clara Oswald were treated with suspicion by Colonel Morgan Blue, under the precaution they could be duplicates. (TV: Into the Dalek)