Kembel

Kembel was a jungle planet near the edge of the Mutter's Spiral, and was considered the most hostile planet in the universe. (TV: Mission to the Unknown) It had lighter gravity than Skaro, (AUDIO: The False Guardian) and was not far from the planet Desperus. (TV: The Daleks' Master Plan)

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 for their activities. (TV: Mission to the Unknown) They transplanted deadly Varga plants from Skaro and also developed other carnivorous plants, such as the rosa toxicaera, to deter visitors on the off chance someone stumbled upon their base and discovered their activities on the planet. (AUDIO: The Rosemariners) They also established a Dalek city with its own spaceport.

Prior to the year 4000, a Galactic Council of representatives of the Outer Galaxies, allied with the Daleks, met on Kembel in order to work out a plan to destroy the Solar System.

Following a sighting of a Dalek ship near the planet, SSS agent Marc Cory set up an expedition to Kembel. He learned of the Daleks' plan, but the two other 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. The planet appeared on the TARDIS scanner screen and Vicki speculated on what was happening there. (TV: Galaxy 4)

Later, the TARDIS materialised on Kembel shortly after departing Troy at the end of the Trojan War. (TV: The Myth Makers) A temporal collision with the Second Doctor's TARDIS diverted the First Doctor from Kembel to Urbinia, creating an alternate timeline. When the Second Doctor averted the collision, the First Doctor landed on Kembel undisturbed. (AUDIO: Daughter of the Gods) Not knowing of the planet or its reputation and having landed the TARDIS 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, who 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 Steven Taylor got it to reverse time, leaving Kembel a wasteland. (TV: The Daleks' Master Plan) After uncovering the plot, Earth sent an expedition to Kembel to arrest Mavic Chen, unaware of his death and the planet's destruction. (PROSE: The Mutation of Time) Additionally, some of the Daleks survived and were sent to the Dalek Asylum where they were classified as insane and placed in "intensive care". (TV: Asylum of the Daleks)

A resort was established later in the 41st century by Zephon, protected by a chronal wavefront that had been generated by the Time Destructor and swept across the planet's surface. (AUDIO: Time's Assassin)

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.

Kembel