Kembel

Kembel was a jungle-covered world near the edge of Earth's galaxy. It was considered the most dangerous planet in the universe.

As Dalek Base
The Daleks reasoned that the most dangerous planet in the universe, where no one would voluntarily land, would make the ideal base. (TV: Mission to the Unknown) It was not far from the nearly as hellish Desperus, a penal colony for prisoners. (TV: The Daleks' Master Plan) They transplanted deadly Varga plants from Skaro to help guard the place. They also established a Dalek city with its own spaceport. Prior to 4000, a Galactic Council of representatives of the Outer Galaxies, allied with the Daleks, met in order to work out a plan to destroy the Solar System, and in particular, Earth.

Following a sighting of a Dalek ship near the planet, SSS agent Marc Cory had set up an expedition to Kembel. He learned of the Daleks' plan, but the two crew members of the ship which landed on Kembel were transformed into Varga plants — forcing Cory to kill them both. The Daleks found and exterminated Cory himself before he could launch an orbital distress beacon to warn the galaxy. (TV: Mission to the Unknown).

By a coincidence, the Doctor's TARDIS had earlier materialised near Kembel before landing there later. It appeared on the TARDIS scanner screen and Vicki speculated on what was happening there. (TV: Galaxy 4)

Later, not knowing of the planet or its reputation and having landed the Ship at random, the First Doctor arrived with his companions while looking for help for Steven Taylor, who had recently suffered an infected wound. They learned of the Daleks' plan, and of the betrayal by the traitorous human Guardian of the Solar System, Mavic Chen. Chen had given the Daleks the taranium they needed to power their Time Destructor. (TV: The Daleks' Master Plan)

Devastation of Kembel
After being pursued across space and time by the Daleks, the Doctor and his friends returned to Kembel. The Time Destructor was activated, and began to accelerate time around Kembel, turning the jungle into a desert. The Time Destructor eventually burnt itself out after it began to reverse time, leaving Kembel a wasteland. (TV: The Daleks' Master Plan) Daleks who survived their encounter with the Doctor here were sent to the Dalek Asylum and were classified as insane. They were destroyed along with the planet. (TV: Asylum of the Daleks)

Behind the scenes

 * Kembel first appeared in the last few minutes of Galaxy 4 as a lead-in to Mission to the Unknown, which did not feature the First Doctor or any of his companions. Following Vicki's statement, a short "teaser" scene to the action of Mission to the Unknown followed.