Rex Salazar, an incurable EVO.

An Exponentially Variegated Organism, abbreviated as EVO, is an organism that has had its intracellular-nanites activated.


Five years prior to the start of the series, a massive explosion released nanites into the atmosphere, infecting every living thing on Earth. These nanites randomly activate inside their hosts, mutating the subjects into monsters known as EVOs.

Besides triggering physical transformations, active nanites can also affect the hosts' minds, turning most EVOs into mindless creatures that know only destruction until they are cured. To combat the EVO threat, the global military force known as Providence was created.

Public reaction to EVOs is varied, with many people viewing EVOs as savage and dangerous. Even EVOs that have retained their sanity are often met with fear and suspicion. Nevertheless, there are people who are willing to peacefully coexist with EVOs, believing they have as much a right to the area as any person as long as the two groups don't bother each other.[1] Some people even attend social events that promote cooperation between humans and EVOs.[2]

Types of EVOs

Human EVOs

Skwydd, Circe, Cricket, and Tuck, examples of human EVOs.

These EVOs are humans prior to their nanites activating. Most barely resemble their original forms and are mindless monsters who will attack anything, including former friends and family.

Although rare, some human EVOs are still aware of themselves and have a relatively humanoid appearance, such as Breach and Quarry. Even rarer are human EVOs who look completely normal as long as their powers remain inactivated, two notable examples being Rex and Circe.

Animal EVOs

A rabbit EVO and its offspring.

Like their human counterparts, animals often undergo dramatic physical changes once their nanites activate. In some animals this transformation also increases aggression. A rarer occurrence is when the animal gains an immense intellectual boost, as in the case of Bobo Haha.

Arthropod EVOs

These are EVOs with arthropod characteristics. They can be dangerous because individual members of the swarm are connected; an entire nest will go EVO if one begins to change.[citation needed] Examples include Swarmers, Lomitle, and Liants.[3]

Plant EVOs

These EVOs were simple plants until their nanites activated. Many become carnivorous after their mutations, such as Blinky, and are able to move their roots and branches at will.

Alien EVOs

Alpha Heatblast, an alien EVO.

This type of EVO is the rarest. While imitating the Ultimatrix, Alpha became several different alien lifeforms. The most notable examples would be Alpha Heatblast, Alpha Four Arms, and Alpha Humungosaur.[4]

Incurable EVOs

Incurable EVOs have nanites that have been changed beyond repair, or have evolved beyond normal curing methods. Examples include Cricket, Tuck, Skwydd, and One. Most seem to have some awareness and possess human-level thought processes.

Virus EVOs

Patient Zero as a full blown virus.

Virus EVOs are microscopic organisms that have been altered by the nanites and developed a form of symbiosis with their host, usually another EVO. They will do anything possible to protect the host, and in turn, to protect themselves. The only example of this bizarre symbiosis is Patient Zero[5] and Peter Meechum[6].

Ghostly EVOs

These EVOs can change into an invisible cloud of nanites. Strong magnets and ice are effective in pulling the EVO back together to be cured.[7]

Genetic EVOs

These are EVOs whose nanites affect or have been affected by dormant traits in their genetics, resulting in unusual mutation patterns. For example, Rex met a small community of werewolf-like EVOs in Mexico. In their case, the nanites had interacted with dormant "Werewolf Syndrome" genes in their bodies, creating an EVO mutation that takes hold at night and reverts at sunrise.[8]

EVO Empires

Many EVOs in the world have banded together to create communities, colonies, and even countries. In a typical EVO empire, one intelligent EVO (an EVO that was able to retain its mind after the EVO transformation and can control its powers) rules by manipulating or controlling the other instinct-driven EVOs to do its bidding. Four EVO leaders have been shown: Quarry, leader of a criminal empire in Hong Kong (later disbanded);[9] NoFace, ruler of the Bug Jar; Van Kleiss, ruler of Abysus; and Serge, leader of Aquania.


Aquania, an underwater city led by Serge.

The largest of the EVO empires, Aquania is located in the North Pacific underneath "Trash Island". The unusual amount of nanites contaminating the waters caused the number of EVOs in the area to skyrocket. Serge, a human EVO who retained both his sentience and sanity, later became the leader of these EVOs. Realizing he had more in common with these new aquatic animals than people, he began to use their natural instincts to build the city out of the garbage that settled there, turning it into coral. He also used EVO anemones to turn plastic garbage into food and energy for the city. Only two people outside of Aquania know of the city's existence.[10]


Abysus, a kingdom ruled by Van Kleiss.

Abysus, the site of the Nanite Event, is home to another EVO empire. The land is filled with an abundance of nanites, and most if not all of the human population living there are EVOs. After the Event, Van Kleiss took control of whatever government was left of Abysus, declaring it a haven for EVOs.

Abysus also has its own army, one made up of a large force of mindless beasts and a much smaller and more intelligent special unit called "The Pack". Despite their formidable strength, Abysus was eventually overrun by Providence as most if not all of its population was captured and collared. Even Van Kleiss' castle was disassembled by the Keep.

Hong Kong

Another empire that had made itself an inconvenience to Providence was located in Hong Kong and run by Quarry, a crime lord. While he did not control the city itself, he was the prominent leader of the Hong Kong underworld. Recognizing the value of EVOs in such matters, he assembled a crime ring comprised of EVOs, which was later disbanded.[9] Quarry tried to resurrect his empire by creating an EVO army with control collars but he was stopped by the effort of Rex and his friends.[11]

The Bug Jar

The Bug Jar, a city ruled by NoFace.

Another EVO empire is located in the city of Kiev, Ukraine, nicknamed the "Bug Jar" by Providence. The city became isolated from the rest of the world shortly after the Nanite Event, when the Earth's magnetic fields funneled a large concentration of unstable nanites into the city, turning the majority of its inhabitants into mindless EVOs. The Bug Jar's massive population was once controlled by NoFace; however, the city has since been transformed into a deserted wasteland after Alpha destroyed all known lifeforms in it.


Providence views Rex as their secret weapon since he has the ability to cure EVOs by extracting their activated nanites. Although the process is generally effective, some EVOs can resist curing,[12] while others are completely unaffected by it.

Due to the limitations of Rex's curing abilities, alternative methods of curing were sought after by scientists. However, various complications led to the information being lost:

  • A serum was developed by Gabriel Rylander that activated dormant nanites. Dr. Holiday stated that if they could acquire the serum, then a cure could be reverse-engineered, but the death of Rylander coupled with the destruction of his lab destroyed the information.[13]
  • A team led by Dr. Holiday and secretly assisted by Zag RS developed a self-deactivation program that, when interacting with normal active nanites, shut them down. The nanites were destroyed when the space station they were developed on was destroyed.[14]
  • A machine was developed that could cure an incurable EVO and succeeded in curing Beverly Holiday before it was destroyed in the process.[15]

Rex eventually used the Meta-Nanites to cure most EVOs in the world before he ordered the nanites to shut down permanently. However, there were still a few EVOs left that escaped the cure.


After losing Rex and overthrowing White Knight, Providence took a different approach in dealing with EVOs. The special collars that had previously been used to suppress EVOs' powers[16] were upgraded, allowing Providence to control the creatures.[17]

However, this technique had several flaws. The collar might malfunction or be destroyed, thus releasing the EVO and returning it to its original mental state.[18] Furthermore, the process of taming the EVO could be agonizing if said individual was not willing to cooperate.[17]


  • The term "EVO" was first mentioned by Doctor Holiday.[19]
  • Some EVOs take on characteristics of completely different species. One example is Father Jose, a human who strongly resembled a cactus.[12]
  • Extreme willpower can overcome EVO madness, as One proved.[20]
  • Apart from Rex himself, Bobo Haha, Biowulf, Skalamander, Van Kleiss and Breach are the only known EVOs to remain after the worldwide cure.

See also


  1. 2.08, "Outpost"
  2. 2.03, "Lost Weekend"
  3. 1.13, "The Hunter"
  4. 3.10, "Ben 10/Generator Rex: Heroes United"
  5. 1.18, "Plague"
  6. 1.2, "String Theory"
  7. 2.09, "Haunted"
  8. 2.13, "Night Falls"
  9. 9.0 9.1 1.12, "Rabble"
  10. 2.02, "Waste Land"
  11. 3.12, "Remote Control"
  12. 12.0 12.1 1.02, "String Theory"
  13. 1.09, "Dark Passage"
  14. 1.14, "Gravity"
  15. 2.15, "A Family Holiday"
  16. 1.17, "Basic"
  17. 17.0 17.1 3.01, "Back in Black"
  18. 3.09, "Assault on Abysus"
  19. 1.19, "Promises, Promises"
  20. 2.06, "Divide By Six"
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