What are they and where do they come from?
The following are theories collated by the officers on Cloudbase and are not confirmed by discoveries.
1. The Origins of the Mysterons
It is widely believed that the Mysterons do not originate from Mars, but from a planet outside of our own solar system. There are several reasons that they could have left their home world - natural disaster or an artificial disaster caused by technological or nuclear destruction of the atmosphere and/or planet. It is even possible that the Mysterons that we know are an observation team sent to watch the people of Earth. All evidence points away from the Mysterons being indigenous Martians, as other indigenous species, such as the Rock Snakes discovered by the first Zero-X crew bear no resemblance to the suggested Mysteron form.
2. The Nature of the Mysterons
There is a lot of evidence to indicate that the Mysterons are not life forms as we understand them. The fact that they were able to rebuild their complex on Mars whilst exposed to the harsh Martian atmosphere suggests that they do not require air to breathe. This theory is also supported by their ability to build the complex on the Moon, which contained no internal atmosphere to speak of. That they were able to survive the attack from the MEV suggests that they have no physical form.
One theory is that the Mysterons are actually a sophisticated and self-reliant computer system that is able to learn and act without an operator. This would explain their cold, calculated action, and their habit of not continuing with a threat once it has been thwarted, as their programming may not allow for them to adapt their techniques. However, it does not explain how they were able to survive the destruction of the Martian Complex, which surely would have destroyed the computer itself, and the machinery that they would require to rebuild the complex using abilities similar to retrometabolism.
Such a complex and powerful computer system would require a large power source in order to allow the signals broadcast to reach Earth. If this is their nature, the power source that they use has not yet been discovered and must be very sophisticated.
Others believe that the Mysterons are non-corporeal beings; thought without a physical body. This would explain their ability to survive the destruction of the Martian Complex and ability to survive in the thin atmospheres of Mars and Earth's Moon. It also explains their apparent ability to travel through space unassisted (Lunarville 7, Shadow of Fear). If, however, they are able to survive in such inhospitable environments, why would they need the protection of the complex at all?
Neither explanation is perfect, and both give rise to the question of why they need agents on Earth. If the Mysterons were computer intelligences, then surely they could access the computer systems on Earth and cause a tremendous amount of disruption. From relatively minor systems such as traffic control systems to control systems for nuclear weapons, computers affect everyone's lives. This would certainly be more effective in destroying all life on Earth than the agents. If the Mysterons are non-corporeal beings, why do they simply not act alone, invisible, undetectable and unlimited in its ability to access anything.
There is also another issue regarding the Mysterons' nature. Are they individual beings, capable of thinking different things, or are they a single consciousness, linked in thought and action? A singular consciousness would explain their inability to understand that Captain Black's actions were not the result of a decision made by humans as a whole.
3. Captain Black
There is one main question surrounding Captain Black's nature. Was he killed on Mars or not? Evidence and general consensus points towards him still being alive. The video log from the Zero-X suggests that the Mysterons used some form of mind control to take over Captain Black whilst they were on the surface. There is a distinct change in both his mannerisms and general appearance on the return journey to Earth. There was never any trace of a body found in the craft, nor any evidence to suggest that one had been ejected into space.
Whilst most Mysterons agents appear the same after reconstruction as before death, Captain Black's appearance has changed considerably. There are those who have referred to him as zombie-like in pallor. Spectrum personnel who have come into contact with Captain Black following his return to Earth have commented on the fact that his eyes, once hazel, are now black and unfeeling. His voice has also changed, becoming more harsh. Captain Black is also well protected by the Mysterons, who teleport him away from dangerous situations that are likely to result in his being injured.
None of these physical changes are present in any other Mysteron agent, suggesting that Black is different in some way to these replicas. The fact that the Mysterons guard him from harm so zealously suggests that he does not have the retrometabolic capabilities of the replicas.
There have been reports from the higher ranks of Spectrum that Captain Black is in fact still alive, and aware of the actions that he is performing against his will. These reports state that the man that he once was has spoken to them, having wrestled control of his body from the Mysterons for a few precious moments, or on occasion, is given it to prevent Spectrum agents from acting against their friend and colleague. These same Spectrum agents also have been heard to make the distinction between the Mysteron agent and his former, trapped self by calling the Mysteron agent 'Black', and the human by his given name, 'Conrad'.
Either way, it remains that Captain Black is different from other agents in that he seems to be controlling the others, and always seems to be in the vicinity when another Mysteron agent is killed and reconstructed. It seems that he is in some way responsible for channeling their power on Earth. Eliminating Captain Black seems to be the best way to cripple the Mysterons in their War of Nerves.