Traditionally the rivals of Gallifrey in time travel technology were assumed
to be the Daleks, with subsequent warmongering races (the Andromedans, Cybermen
and Sontarans) mere pretenders through theft or acquisition. After The
Apocalypse Element however Big Finish levelled the playing field,
introducing new races already equipped with temporal tech (the Monan Host,
whose world was created through a temporal accident), and later including one
from the Doctor Who Monthly comic strip in the Warpsmiths of Phaidon.
Order within the Vortex is maintained by a formal agreement between such
temporal powers to protect lesser races from threat and enforce a moratorium on
time-travel experiments.
By the time of Big Finish's Gallifrey series, which is assumed to follow
from the events of Zagreus the Sunari and Nekkistan groups are also
included, likewise featuring time travel as their raisen d'etre. Power blocs
formed, with the Monans, Nekkistani, Unvoss, and Warpsmiths comprising a
fragile coalition of temporal powers. In order to counteract this President
Romanadvoratrelundar initiates the creation of a 'temporal bubble world' called
Gryben which attracts unauthorised timeships to it and acts as a vetting centre
for those cultures petitioning to join the temporal race — those rejected and
unable to return home are detained indefinitely on the planet, essentially
turning Gryben into a refugee centre and massing point for temporal tech
dealers and a resistance group calling itself Free Time (other races within
Free Time variously include Gallifreyans, humans, and Yevnons alongside the
Monan Host). Free Time's philosophy that no one power should have authority
over time and that it belonged to everyone falls foul of Gallifrey itself,
which then employs the Celestial Intervention Agency (and its Vortex Ops units)
to monitor the group's activities.
Such is the state of politics that inform some of the background detail of
Big Finish's stories of 2005; in Medicinal Purposes antagonist Knox has
acquired a TARDIS from a Nekkistani dealer on Gryben, and it is a vessel of
Nekkistan origin which is retconned into the beginning of Storm Warning
by the events of Terror Firma. It could be assumed that the rising
tensions between Gallifrey and its rivals (not excluding the Daleks of course)
and foresight of increased access to temporal technology provokes Gallifrey to
conduct the experiments referred to in Unregenerate!
The finale (one resists the urge to call it a conclusion) of the Gallifrey
series sees temporal catastrophe envelop Gallifrey, and the not-refuted
suggestion by fans that the Time Lords' oldest rivals, the Daleks, eventually
exploit this instability. This loosely accommodates the suggested Gallifrey/
Dalek Time War referred to in the new TV series, and to date Big Finish seem
happy to leave it there.