Quirks

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You can find more information at: MHA Wikipedia


The first person in the world to manifest a Quirk was a newborn baby in Qing Qing City, China; the baby had the ability to emanate light from their body.

After that phenomenon, many people around the world began to manifest different kinds of superpowers. While the cause of the Quirk phenomenon is unknown, it has been theorized that the development of Quirks was caused by the spread of a virus carried by mice. These superpowers were first referred to as Meta Abilities before later being called Quirks.

The dawn of this extraordinary era was marred by a breakdown of society caused by the sudden onslaught of criminals empowered by their newfound "superpowers" and ordinary people being prejudiced against the Quirk users.


The era of Vigilantes.

As chaos and unrest ensued due to the outbreak of Quirks, ordinary civilians with their own Quirks decided to take matters into their own hands to bring order to society and thus the first "Heroes" appeared in the form of Vigilantes and thus beginning the Vigilantes Era.

During this time period, All For One became a symbol of unity in society. He used his Quirk to remove Quirks from those who did not want them and give Quirks to those that did. His actions under the guise of returning society to its prior state of humanity, when in reality, he was gathering followers who were loyal to him, allowing him to act out his ulterior motives.

As society adapted to the new status quo, the Police Force moved to prioritize leadership and to maintain the status quo, and as such, decided not to use Quirks as weapons. To fill that void, the profession of crime-fighting Quirk users, Pro Heroes, began to exist which caused the Vigilantes to slowly disappear. Authorizing the use of powers that could so easily kill, however, was a greatly criticized decision at first.

Over time, it came to garner public support due to the fact that the first people to work professionally as heroes acted morally and upheld the law.[6] However, some members of society were not happy with the governments' regulations on Quirk usage as they believed that the free use of their superhuman abilities should be a basic human right.

A group of Quirk users known as the Meta Liberation Army, led by Destro, had tried to stop the passing of regulations that would restrict Quirk usage. They rebelled against the governments of a number of nations for several years before ultimately suffering defeat.[8]

Currently, roughly 80% of the people who make up the global population possess a Quirk.  

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Information

Quirks are said to be the next stage of evolution in the human race. It is possible to diagnose a person as possessing or lacking a Quirk by analyzing the presence or absence of an extra joint in their pinky toe. People with only one joint will develop a Quirk while having two joints indicates that the person is Quirkless.

A person's Quirk will normally manifest around the age of four years old, although, it is possible for a child to be born with their Quirks already manifested, such was the case with Present Mic and the very first person to manifest a Quirk, the Luminescent Baby.
((Shoto's overuse of his Quirk gives him frostbite.))
Although easy to forget, the fact is that Quirks are physical abilities. As such, they can be trained and worn out. When a person works out their muscles, the muscle fibers are destroyed and new, stronger ones grow back; this same rule applies to Quirks. However, should a Quirk be overused, the user could suffer any of a variety of drawbacks, depending on the nature of the Quirk. These drawbacks are usually simple ailments, such as dry skin or nausea; however, in some cases, the drawback can be much more severe.

There are also instances where a Quirk doesn't suit the user's body and the body can't handle it. Some people, such as Yuga Aoyama, suffer from birth defects that cause the victim to have difficulties controlling their Quirk. Such conditions can be bypassed through the use of support equipment, such as Yuga's belt. Similarly, Nine suffers from chronic pain and cellular degeneration due to the massive strain of his Quirk, Weather Manipulation.

Quirk levels can be measured, though only Toshinori Yagi's have ever been shown, being at 15,000 AP at his peak and reaching a low point of 2,500 AP in the present.

Although very rare, it is also possible for animals to possess Quirks, such as Nezu having a Quirk that gives him above-human intelligence.

Every Quirk contains an echo of the consciousness of its wielder; if a person's Quirk is transferred to someone else, the consciousnesses of the previous wielder will appear in the new user's mind, either as voices in dreams or manifestations in a mental mindscape. If further transferred to yet another new user, then that new user will experience the consciousnesses of all of the previous users. Though, these consciousnesses will disappear if the new user loses the transferred Quirk.  

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Quirk Factor

The term "Quirk Factor" refers to the collective physical and genetic traits that compose a person's Quirk. This includes the primary Quirk power as well as all the biological mechanisms that allow said primary power to function properly. Quirk Factors also contain a person's consciousness.

Under special circumstances, a second Quirk can be added to a person's genetics. There is a chance that the two Quirks may merge, becoming a new Quirk, as was the case with One For All.

Certain Quirks, such as Erasure, are capable of temporarily halting the expression of the Quirk Factor, rendering the Quirk unusable for a short period, but not affecting the Quirk Factor otherwise. There are other Quirks, however, that are able to directly damage the Quirk Factor of a target, preventing the Quirk from being activated until the user manages to naturally recover. It's also possible that a Quirk Factor can be damaged beyond recovery, causing the Quirk to be permanently suppressed.

The first instance was when Eraser Head was severely injured by the U.S.J. Nomu. Eraser Head’s body sustained a large amount of damage, especially his face and head, and this caused his Erasure Quirk to have a much shorter time limit, as he has to blink more often because of the damage he took.  

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Heredity

An example of Quirk heritage of two families.

Quirks are inherited genetically through what appears to be Mendelian inheritance. A child will either inherit the father's Quirk, the mother's Quirk, or a new composite Quirk formed by a fusion of the two. This composite Quirk may sometimes give the appearance of the person having two separate Quirks, such as Shoto Todoroki's Half-Cold Half-Hot.

Much more rarely, in the case of Eri's Rewind and Tomura Shigaraki's Decay, a child may manifest a Quirk that is entirely unrelated to their genetic lineage, akin to a mutation.

Physical abnormalities caused by Quirks can be passed on to the next generation, even if the Quirk that causes the abnormality is not passed on; Fumikage Tokoyami has a bird-like head that has nothing to do with his shadow monster Quirk, Koji Koda has a jagged, rock-like head that has nothing to do with his power to talk to animals, and Mina Ashido has a pair of horns and eyes with black sclera instead of white, that has nothing to do with her power to produce acid.

There is also a possibility that two people with Quirks will have a Quirkless child, such was the case with Izuku Midoriya.  

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Quirk Marriage

Since Quirks are passed on from parent to child, some people choose a marriage partner based on their Quirk. This is what's known as a Quirk Marriage.

The idea is for the child to have a powerful Quirk that combines the parents Quirks.

A popular example of this is Shoto Todoroki and his Quirk, Half-Cold Half-Hot which is a combination of his father's Quirk, Hellflame and his mother, Rei Todoroki's ice Quirk. Powerful combinations are not guaranteed, even from strong parents - Shoto was the only one of four siblings to have a powerful combination of the parental quirks without downsides.  

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Quirk Frequency

Some Quirks are very common, in that many people possess Quirks that fall in that particular classification. Known classifications of common Quirks include:

Gigantification: Quirks that allow the user to increase the size of ones self.
Other Quirks are very rare, in that not many people possess Quirks of that nature. Known classifications of "Rare Quirks" include:

Warping: Quirks that allow the user to teleport themselves, other people, and/or objects to a different location.

Regeneration: Quirks that allow the user to heal from severe damage quickly.

Elemental: Quirks that allow the user to bend one of the 4 key elements. Fire, water, earth, and air.  

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Awakening

After initial Quirk manifestation, it is possible for the user to undergo an "Awakening". The right catalyst can cause Quirks to evolve on the spot. This results in ones Quirk gaining a new level of strength and/or new aspects to its nature that were previously not possible.

An example of this phenomenon is demonstrated when Himiko Toga's disguise Quirk evolved in a life-or-death situation, giving her the ability to duplicate the Quirks of the people she transformed into, shown when she used Zero Gravity while she had taken the form of Ochaco Uraraka. It is also said that Geten's Quirk evolved when Re-Destro burned himself, from the solely manipulation of ice to being also able to change its temperature.