Doctor Who: Event 2016 - Supremacy of the Cybermen — Cavan Scott

Exiled from Gallifrey at the very end of Time, Rassilon, fallen leader of the Time Lords, has been captured by the last of the Cybermen. Now the Cybermen have access to time travel. With it, every defeat is now a victory. Every foe is now dead -- or Cyberised. 
The Legions march across time and space, leaving devastation and converted civilisations in their wake, their numbers growing with every world that falls. Evolving. Upgrading. Reconfiguring. All seems lost. Forever.

Can the Ninth, Tenth, Eleventh and Twelfth Doctors - each battling the Cybermen alone, on a different temporal front - undo the damage that has been wrought on the universe, before they are converted themselves? Or is this how the universe dies? Not in fire, but in cold, unfeeling metal...