The story is noted for David Banks and Mark Hardy reprising their respective roles of the Cyber-Leader and the Cyber-Lieutenant for the first time for Big Finish, and for the first time in performed Doctor Who since Silver Nemesis 30 years earlier.
The Cybermen have been patient, setting their plans in place over a number of years. As the final stage is implemented, in the darkest hour, the Doctor must identify who among his allies he can trust.
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- The Doctor - Colin Baker
- Cyber Leader - David Banks
- Cyber Lieutenant - Mark Hardy
- Riva - Frog Stone
- Daniel Hopkins - Blake Harrison
- Atriss/Bill Parker/Captain Weaver - Wayne Forester
- Lewis Price/Kel - Russ Bain
- Riva, Atriss, and Kel are Veridians from Veridia.
- Hopkins lost his family five years ago. He encountered the Cybermen four years ago.
- The Cybermen's attack on Veridia, where they killed or converted tens of thousands of Veridians, occurred three or four years ago.
- Cyber-conversion begins with changing the biological chemistry of the subject, increasing adrenalin and endorphins.
- The Cyber-Force is a typical Cyber-Fleet of at least twenty Cyber-Warships, with a conservative estimate of two hundred thousand Cybermen. They hide on the sea bed beneath the Atlantic Ocean.
- The flagship contains Cyber-Control.
- The Cybermen use a shuttle.
- Cybermen measure time in "cycles."
- Each warship has several vaults, each holding at least a thousand cyber-pods, which serve as hibernation units.
- Water is a compound of hydrogen and oxygen. The Cybermen's weapons evaporate hydrogen molecules.
- The Cybermen broadcast a message in all languages to everyone on Earth, giving them one hour to surrender.
- Cyber-nanotechnology is sentient. UNIT does not have the capability to detect cyber-technology.
- Recording of this story took place on 15 and 16 November 2017 at The Moat Studios.
- A trailer for this story was released 4 May 2018.
- Warlock's Cross takes place in 1994, dating The Helliax Rift to 1984. The original mission to Warlock's Cross occurred in 1987, just after Daniel lost his family, which was five years before Hour of the Cybermen, dating this story to 1992.
- The Doctor hopes that dinosaurs are not responsible for a deserted London again. (TV: Invasion of the Dinosaurs)
- Price and Hopkins reference previously meeting the Doctor in his fifth incarnation. (AUDIO: The Helliax Rift)
- The Doctor mentions that Cybermen have utilised the poles before. (TV: The Tenth Planet)
- The Cyber-Leader immediately identifies the Doctor. (TV: Silver Nemesis)
- The Cybermen are of the design identified by ArcHivist Hegelia as "CyberNeomorph". (AUDIO: The Ultimate Cybermen)