Evolution chamber

The evolution chamber, sometimes referred to as the forced evolution chamber, the accelerated evolution chamber, or simply the test tube, was a zone on the planet Bortresoye in the Divergent Universe. (AUDIO: Scherzo, The Next Life). Unlike the other zones, which were typically populated landmasses (AUDIO: The Creed of the Kromon et al.), the evolution chamber took the form of a totally closed off "test tube", a circular, glass construction, only inhabited by its test subject. (AUDIO: Scherzo) The Interzone could be accessed through it if the glass was broken. (AUDIO: The Creed of the Kromon)

Appearance
The evolution chamber was a circular glass "test tube", lit with a blindingly bright white light. It was otherwise featureless. It had absolutely no scent whatsoever. (AUDIO: Scherzo, The Next Life)

History
The evolution chamber was initially constructed by the Divergence, a species which Rassilon banished to the Divergent Universe in fear that they may one day rival the Time Lords if they remained in N-Space. They created the chamber in an attempt to manipulate evolution in order to create a species capable of breaking the time loop and escaping the universe. (AUDIO: The Next Life) However, this plan was disrupted when the Eighth Doctor was banished to the same universe, with Charlotte Pollard following him. They arrived in the chamber, and began talking, leading to the sound of their voices evolving into a living intelligence, which became the dominant life form in the chamber, taking over from the creature that was intended to evolve there, which itself evolved into a composite being of the Doctor, Charley, (AUDIO: Scherzo) and the Divergence, and became Daqar Keep. (AUDIO: The Next Life)

The Doctor and Charley spent weeks trapped inside the chamber, constantly walking without succumbing to exhaustion. The being created from the Doctor and Charley's voices, which was dubbed the "Sound creature" by the Doctor, attempted to out-evolve the Doctor and Charley, but they managed to evolve fast enough to keep up with it by merging themselves into a single being. The sound creature tried to convince the Doctor and Charley to sacrifice themselves for it, but, while the Doctor was ready to, Charley refused, and, since they were merged into a single being, this could not happen without their mutual consent. Once the sound creature was defeated, the Doctor and Charley silenced it, chose to not to kill it, left it behind, (AUDIO: Scherzo) and left the experiment, (AUDIO: The Creed of the Kromon) followed, unknown to them at the time, by Daqar Keep. (AUDIO: The Next Life)

The Doctor, Charley, and C'rizz later encountered Daqar Keep himself, who had allied himself with the Divergence and Zagreus against Rassilon and the Kro'ka. During the course of the adventure, Daqar Keep married Zagreus, and Rassilon and the Kro'ka were banished to the evolution chamber, forced to repeat the same actions as the Doctor and Charley had, for eternity. (AUDIO: The Next Life) However, at least the former was known to have returned to N-Space by the time of the Last Great Time War. (TV: The End of Time et al.)

Properties
The evolution chamber had some unusual properties. It could, as the name implied, accelerate evolution. It also caused almost total sensory deprivation. The Doctor and Charley lost all their senses except hearing within it, including their ability to sense time. It also functioned as a sort of crude life support, with the Doctor and Charley not needing to sleep, drink, or excrete at any point despite spending weeks in the chamber, although they did still require food, which the sound creature provided for them in the shape of the alien that was initially intended to evolve in the chamber, and would later become Daqar Keep. (AUDIO: Scherzo)

Other references
The Doctor and Charley recalled their ordeal within the chamber at multiple points during their subsequent travels through the Divergent Universe. (AUDIO: The Twilight Kingdom, Faith Stealer)