Reconnaissance scout

Reconnaissance scouts, or recon scout Daleks, were the specialised Daleks who were first sent out from Skaro to scout out new planets in preparation for invasion.

Nature
Reconnaissance Scout Daleks possessed a number of abilities normal Dalek soldiers lacked, the Dalek creature having been "specially advanced from the basic Dalek". If stripped of its casing, the dark-green, oily Reconnaissance Scout mutant could possess other lifeforms like humans by sticking to their back, piercing the skin and using its tentacles to integrate itself into the central nervous system of the creature and form a mental link to control its host. If it was cut up and divided into pieces then the mutant could be restored to life by ultra-violet energy and teleport the pieces back. Reconnaissance Daleks were also capable of remotely disrupting the Doctor's TARDIS' circuitry and disabling their sonic screwdriver. (TV: Resolution)

History
One such Dalek arrived on 9th century Earth, becoming possibly the first Dalek ever to arrive on the planet. It was defeated by an army of humans on British soil in the Battle of Hope Valley. The mutant was divided into three pieces by the Three Custodians, while its casing was destroyed. Some parts of the casing remained, and the third Custodian did not complete his journey to the burial site in Yorkshire.

This part, recovered by archaeologists in Sheffield, was exposed to ultraviolet light and the energy restored it. The mutant was able to possess Lin and forced her to rebuild its casing using what was left from the 9th century and Earth supplies from a farm owned by a man it killed named Dinkle. It continued its mission in preparing Earth for an invasion from the Dalek Fleet.

The Dalek was finally defeated when the Thirteenth Doctor jettisoned it into a supernova. (TV: Resolution)

However, fragments of its DNA survived inside of the Dalek's melted casing and was cloned by human scientist Leo Rugazzi. This inadvertently resurrected the Dalek because a Dalek's consciousness can survive in even the tinniest fragment of their DNA. The resurrected Dalek constructed a new race of Daleks and intended to conquer Earth and use it as a base to take over the universe. However, the Doctor summoned Death Squad Daleks to put down the revolution. As the new Daleks DNA was corrupted due to their human origin, the other Daleks saw them as impure and exterminated the new Daleks. The Recon Scout who attempted to convince the other Daleks that he had mutated in order to survive and to purify his DNA instead to no avail. The Death Squad Daleks exterminated the cloned Recon Dalek, destroying it for good. (TV: Revolution of the Daleks)