The Eternity Cage
John Hurt (The War Doctor), Jacqueline Pearce (Cardinal Ollistra), , Honeysuckle Weeks (Heleyna), Timothy Speyer (Kruger), Helen Goldwyn (Professor Crane), Gunnar Cauthery (Kavarin), Matthew Cottle (Leith), Dan Starkey (General Fesk/Sontarans), Josh Bolt (Kalan), Barnaby Edwards (Vassarian), Andrew French (Muren) and Nicholas Briggs (Dalek Time Strategist/Daleks)
Sontarans are the ultimate warriors – so they believe – and the Time War the ultimate conflict. Denied that glory by Skaro and Gallifrey alike, General Fesk of the Eighth Sontaran Battle Fleet employs a dangerous strategy to draw both sides to the planet Rovidia and prove his forces worthy…
Meanwhile, the War Doctor leads a rescue mission, aided by Rovidian street-urchin Kalan. Neither Daleks nor Time Lords expect the Sontarans to be so fearsome a foe, until they uncover the secret of the Eternity Cage.
The Dalek Time Strategist and Ollistra mention Narvin sending the Fourth Doctor to avert the creation of the Daleks. (Genesis of the Daleks, Ascension)
The Sontarans are trying to participate in the Time War. (The Sontaran Stratagem; Sontaran Ordeal)