• Cybermen have developed on multiple worlds – Mondas, Telos, Earth, Planet 14 and Marinus – as a result of parallel evolution. There is no evil plan or evil genius behind their creation: they just happen wherever there are people.
• After the Master’s resurrection was corrupted, he became physically unstable, intermittently transforming into a creature of pure energy. This condition was cured by the Time Lords on Gallifrey but he left his home world by mutual consent after acquiring a new TARDIS.