The Mysterons are a race of disembodied entities from the television series Captain Scarlet And The Mysterons. They have no known physical identity, their only form of appearance being through two green "eyes". They are capable of communicating in English with Humans, via radio and other means. They have perfected the ability to reverse matter (also known as Retro-Metabolism), which is demonstrated when Captain Black destroys their Martian Complex after mistaking a surveillance camera for a weapon and concluding that they are under attack. Having destroyed the city, the Mysterons rebuild it in a matter of seconds before declaring a War of Nerves against Earth for the unprovoked attack, vowing that they will destroy all life across the planet.
The Mysterons prove capable of recreating perfect replicas, but to do so, the victims must first be killed. Captain Black was the first of those replicated, becoming their Chief Agent on Earth after returning from the Mars mission and promptly disappearing. Acts of war committed by the Mysterons include 'killing' Captain Brown and Captain Scarlet - the former they converted into a walking bomb, whilst the latter became 'indestructible' - in addition to sabotaging air conditioning systems, and plotting the death of fashion designers and heads of state.
A Mysteron city was located on the far side of Mars, away from visible sight. The city was discovered by Spectrum in 2068, after mysterious signals had been traced back on Earth.