Axista Four

 was a previously-uninhabited planet colonised by the Tyrenians and then humans during the 25th century.

Colonisation
When the Earth Federation outlawed genetic engineering circa 2439, Stewart Ransom organised the escape from Federation space of the Tyrenians, genetically-modified human super-soldiers with canine features created by his colleague Gustav Tyren. The vessel took the Tyrenians to the uninhabited Axista Four, where they established their own settlement.

In that year, Axista Four was also chosen by Ransom an as ideal planet to establish an Independent Earth Colony. The colonisation was part of the Back to Basics movement, which argued that humans had grown too reliant on technology since the 20th century. 5,000 human colonists travelled to the planet in The Big Bang. Ransom did not know the Tyrenians had already settled there, having mistakenly used the same raw data to select the planet that he had used to program the Tyrenian escape vessel.

As a result of the mix-up, initial probes of the planet by the Federation discovered the Tyrenian presence and Ransom was instructed to wipe them out. Overcome with guilt, Ransom allowed his ship to be shot down by Tyrenian defence satellites. The ship crashed, killing many of the colonists, including Ransom, and leaving others, like his daughter Kirann, trapped in suspended animation without the medical experts to safely release them. While much of the details surrounding the crash were unknown to future generations of the colonists, the event became remembered as Planet Fall Day.

Federation Battledroids, which Ransom had intended to dispose of on landing, were activated after the crash and attacked the Tyrenian settlement, sending the survivors into hiding. The surviving human colonists built a settlement, Plymouth Hope City, modelled on those of the Old American West due to their commitment to the Back to Basics principles.

26th century crisis
In the early 26th century, Tam Kartryte was elected Acting Leader of the Colony. A proponent of the Loyalist faction, he resisted calls from the Realist faction to abandon the principles of the Back to Basics movement on which the colony was built, while the Realists argued that the colony was slowly dying as a result of adherence to those principles. In practise, the Back to Basics intentions had been taken to the extremes; the movement sought to build a settlement less reliant on technology but not one completely devoid of it.

Despite the colony's independent status, in 2539, Earth forces intended to resettle 80,000 refugees who had been displaced by the wars against the Daleks, which the underdeveloped colony could scarcely accommodate. The Second Doctor, Jamie McCrimmon and Zoe Heriot visited this colony during the crisis and discovered the Tyrenians had claimed the planet first. The Doctor revived Kirann Ransom from suspended animation and she became the new leader of the colony, uniting Loyalists and Realists behind her and clarifying the Back to Basics philosophy.

War between the humans and Tyrenians threatened the colony when the hibernating Tyrenians began to revive but the Doctor negotiated a peace settlement. They also foiled a plot to reactivate the battledroids and wipe out the colony outright, allowing the incoming refugees to start afresh. After the crisis, Earth forces agreed that, after the arrival of the refugees, the human and Tyrenian colony would be left in peace.

Later history
The Seventh Doctor told Ace that, according to legend, Ransom's colony "had a long and happy existence; a really successful venture."

Millions of years later, in the far future, Axista Four went nova, becoming a fireball. (PROSE: The Colony of Lies)