What is the main setting in the novel, Doctor Who: The Five Doctors?

The action takes place primarily in the Death Zone on the Time Lords' home planet, Gallifrey, and in the Dark Tower that houses the tomb of Rassilon, the first of the Time Lords. The Death Zone is a bleak and blasted place. At one time, corrupt Time Lords had snatched warriors from their proper times and places, setting them in the Death Zone to battle to the end.