The Viruses are a species of sentient techno-organic beings whose leader are Alpha. They are capable of infecting from living beings, such as humans and animals, to electronic devices. They seek to conquer the world by infecting and taking over their hosts by transforming them into grotesque montrosities. They are currently being commanded by Dollmaker, Black Angel, Queen Zenoria and other three unknown commanders.
After Alpha's physical form was destroyed, he needed to find a host in order to become stronger again. After he landed on an unknown planet, he found Queen Zenoria, whom he instantly attached to and managed to infect her. The first kind of Viruses were created by Zenoria herself, who used to corrupt the life of her own planet and destroy her own family.
Years prior to the series' events, Alpha goes to Earth through a meteor and is found by an organization of scientists who studies his life form and find out about his incredible properties which would be capable of improving the human life.
The virus are capable of infecting humans and once they do, the term Infected is given to them. They tend to infect people who are emotionally unstable, as they feed themselves on negative emotions. Once they infect a human, they enhace their physical capabilities and give them unique abilities. At first they are presented to their preys as allies, but over time, they slowly are taking control of their host and make them generate more and more negative emotions until they completely absorb their host. Once this happens, the virus evolves and generates an armor around the host's body. This state can be only reverted if their energy core is destroyed, which is located on the host's chest.
Their weak spot is their energy core, usually located on the chest of the host. If it is destroyed, the virus will lose its hold on the host and will be ultimately defeated.
There are also stronger versions of viruses known as Ultra-Virus, who are capable of infect a person and start infecting more poeple and create minions, similar to zombies. Examples are Amare and Pluma. These virus are also harder to defeat and are likely to survive if their energy core is broken.
If the infection is not reverted in time, the Virus will eventually consume its conscience and slowly transform the host into a machine by firstly destroying its brain and completely take control of the body.
The Guardians' Viruses are the only known completed creatures that were developed. Unlike the Viruses produced by Dollmaker, they can live many years without a host and once they bonded with Brian and his friends they could choose to take them over or to ally with them. Due to their programming, they ended up choosing the later. They do not feed onto the user's emotions and are inside of their bodies, not being capable of being seen at naked eye. After the used said "Rise!" (plus the name of their respective guardian), the user's body is covered in light blue energy and armor pieces are generated and placed onto the host's body. The energy serves as a secondary armor that protects the user in case if someone forcefully attempts to separate the person and his guardian. According to Brian in "Into The Darkness Part Two", it felt like his skin was being pulled off when he was being separated from Myles.
They have the ability of generating armors and weapons that the Guardians uses to fight against threats. Besides, the armor and its weapons are adaptive, being capable of assimilating other forms of weapons and develop their own version or create different types of armors - a process called as "Viral Mode", which consumes lots of the user's energy, yet it makes the person much stronger. Additionally, the Virus is responsible of maintaining the health of the user, as it constantly monitors its body to check if everything is alright. In case a member of the body is broken in battle, the Virus can easily regenerate the broken limb.
The Virus are a race of sentient creatures currently commanded by six Infected, while three of these are active. As result, their appearance may vary depending on which vertent of Alpha they belong to. Once a Virus is created, he/she has a short lifespan and needs a host in order to survive. After it finds an appropriate host (generally those who have large amounts of negative feelings), it links with he or she and weaponizes the host. Overtime, they will influenciate the user to become more and more violent to the point where the Virus take the control of the host's body. If their energy core is not broken in time, the creature will permanently absorb its host and transform him or her into a living weapon of mass destruction.
There is a superior kind of Virus known as Ultra-Viruses who are created with larger amounts of energy and are much stronger than regular Viruses and are likely to survive if their enerhy are broken. They are capable of infecting other people to create minions similar to zombies. These viruses also can create everything that comes up on the mind of their host and can take control with more ease unlike the regular Viruses. Dollmaker creates these when she feels that her target has much hatred and pain inside of him or her.
There is also a special kind of Virus created especially to Dollmaker's Gladiators, who act more like Brian and his team's super powered armors instead of vicious parasites. Nonetheless, they still do share the same aspects as the rest of the Viruses, as they influenciate the user to generate more and more negative feelings to feed them.
In order to neturalize the parasite, their energy core must be broken otherwise they completely take control of their host. The Techno-Killers have developed weapons to handle them, which quickly destroys the Virus but makes the host go through lots of pain. Additionally, if the host dies while the Virus is inside of them, the parasite will end up consuming their body until there is nothing left, as they have nothing to feed (such as negative feelings).
Additionally, the Viruses reproduce assexually, being capable of spawning creatures either forcefully (through artificial means) or by their own will, which is the case of the Ultra-Viruses, being capable of spawning more of themselves in a small amount of time to infect other peple.