Death Zone
The Death Zone was an area of Gallifrey used during the Dark Times when Time Lords pitted various combatants against each other in the the Game or the Game of Rassilon, even though Rassilon himself would put a stop to the proceedings.
History
The Time Lords had used a time scoop to pull beings out of time and place them in the Death Zone, where they would play "the Game" and try to destroy each other. Daleks and Cybermen were never allowed to play "the Game" because they played too well. From a control room located within the Capitol, only accesible by playing the right tune on the Harp of Rassilon, a person could activate and use the time scoop to capture beings. When a being had been captured, a figure of them would be created and the figure would be placed somewhere on a model of the Zone, and wherever the figure was placed is where the being would materialize. From the Capitol, the High Council possessed a secret transmat system that was linked to the Death Zone and to the Tomb of Rassilon, which was located in the Zone. However, the transmat system needed activation from the Tomb of Rassilon side, so a time in remained inaccessible.
Lord President Borusa re-activated the Death Zone. Not knowing Borusa's treachery and only that the Game of Rassilon had begun again, the High Council of Time Lords sent at least one investigator, who died quickly without finding out anything. Borusa made the first, second, third and fifth incarnations of the Doctor play the Game. (When Borusa tried to time scoop the Doctor's fourth incarnation and Romana, he found himself unable to do so because of a time eddy.) He also transported Susan Foreman, the Brigadier and Sarah Jane Smith separately, while Turlough and Tegan Jovanka remained with the Doctor's fifth incarnation in the TARDIS. Together, as Borusa had planned all along, they braved the Death Zone and managed to find the Tomb of Rassilon safely. Meanwhile, the High Council of Time Lords had recruited the Master to retrieve the Doctor safely out of the Death Zone.
As opponents, Borusa time scooped a Dalek, a squad of Cybermen, a Raston Warrior Robot and a Yeti.
Ultimately, Borusa hoped to use the enemies to misdirect the Doctor's incarnation for his real purpose of securing the Tomb of Rassilon, which he believed held the secret of immortality (DW: The Five Doctors).
The renegade Time Lady Iris Wildthyme once encountered a variety of third-rate foes which including Zarbi and Quarks. (EDA: The Scarlet Empress)
Physical environment
The Death Zone had mountains, marshes and at least one paved road. The fog was thick so one couldn't see where one was going and red thunderbolts continuously fell from the sky which would kill instantly. (DW: The Five Doctors) It was about the size of North Wales, despite those on Gallifrey believing it to cover a great distance. Both Iris Wildthyme and the Doctor know this. (EDA: The Scarlet Empress)It also strongly resembles Wales rather than the usual Gallifreyan landscape.
