Life Fibers

Life Fibers are sentient parasitic organisms of extraterrestrial origin, and are the origin of all clothing on Earth, as well as the entities responsible for the evolution of humanity. All Life Fiber originates from the Original Life Fiber, also known as the Primordial Life Fiber, an object originated from space that crashed onto Earth tens of thousands of years ago.

The Original Life Fiber was supposedly destroyed when Ryūko Matoi and the S.S. Naked Sun cut through its core in episode 23. In episode 24, it approached Honnōji Academy in a liquefied form and wrapped itself around the missile that was in the center of the academy. It was torn off the missile by Ira Gamagōri and the missile was destroyed by the Nudist Beach's "Ultimate Double Naked DTR." Ragyō Kiryūin told Nui Harime to "cast her body away," allowing the Original Life Fiber to latch on to Nui's lifeless head and absorb it. Nui then took control and "wears" the Original Life Fiber in which Ragyō then absorbs it and morph herself to a missile, where she use it to go to the REVOCS satellite in space. The Original Life Fiber is completely depleted from existence when Ryūko takes "Absolute Domination" for herself, eliminating Ragyō's Shinra-Kōketsu.

History
Shortly after the Original Life Fiber appeared on Earth, Life Fibers began living as parasitic life forms, gaining sustenance from the biological life energy of other organisms. However, since the host could not withstand the strain of having them in their bodies, the Fibers began covering the host instead. As such, they targeted the ancestors of today's humans, which were the species with the most well developed brains at the time, and started accelerating their evolutionary process. With time, Life Fibers entered a dormant state, but left mankind with the evolutionary instinct to cover themselves. Twenty years before the events of the main story, Ragyō found the Original Life Fiber, causing the Life Fibers to awaken from their stasis, seeking to feed on human life.

Biology
Life Fibers are extraterrestrial organisms, originating from deep space outside of the Solar System, and possibly outside of the galaxy. Their evolutionary history is unknown, but they are unique creatures that are vastly different from any form of life on Earth.

Life Fibers are multi-cellular microorganisms whose bodies grow in long thin strands, which radiate bright red energy. These strands are very durable, being stronger than most materials found on Earth. Life Fibers also possess a regenerative factor and in some cases (predominantly in complex organisms composed fully of or enhanced with Life Fibers) will reform into a whole even after being cut all the way through, though this process can be stopped if they are cut from two sides simultaneously in a scissoring motion. Life Fibers are parasitic organisms, living off the bio-energy that exists within the cells of the nervous system as well as in the circulatory system. In order to maximize the longevity of a host, they cover their host's body and bind to their peripheral nervous system instead of inhabiting their internal organs.

The presence of Life Fibers can alter their host's DNA, which is how humanity evolved large brains, and is possibly how Goku Uniforms can give superhuman powers. Life Fibers also seem to be self-aware entities, capable of making decisions and thinking. Life Fibers seem to be incapable of talking to their hosts, with the exception of Ryūko, who can communicate with her Kamui, Senketsu. This is due in part to Isshin Matoi imbuing the fibers with Ryūko's genes. Life Fibers are also capable of manifesting new abilities in response to certain stimuli (usually life-threatening situations). Their ability to rapidly evolve is one reason why they are considered dangerous.

Life Fibers reproduce across the galaxy through a series of steps. After finding a planet with intelligent life suitable for their purposes, they begin subtly manipulating the evolution of a select species, creating a race that will become the dominant species on the planet. Once the selected species has dispersed across the planet and reached a certain stage of evolution, the Life Fibers will begin taking control of that species on the planet. When enough members of the species have been taken over by Life Fibers, the aliens will take control of their hosts and rise into the stratosphere, creating a massive "cocoon" of Life Fibers that envelops the entire planet. This is known as the Celestial Cocoon Seed Planet, Cocoon Sphere Genesis, or Starseed Cocoon Sphere. In this form, the Life Fibers consume the planet's thermal energy to create new Life Fiber seeds. Once enough seeds have been created, the Life Fibers will cause the planet to explode, scattering the new generation of Life Fibers all across the cosmos in a kind of galactic diaspora.

Use as a Material
Life Fibers are widely used in the production of clothing such as Goku Uniforms and Kamuis, although a small amount of Fibers are present in all clothing produced by Revocs Corporation, which accounts for 90% of the global market (As of episode 21, 100% of the global market). In Honnōji Academy, One-Star Goku Uniforms are composed of 10% Life Fibers; Two-Star Uniforms, 20% and Three-Star Uniforms, 30%. Kamuis are made entirely of Life Fibers. Hōka Inumuta is in charge of analyzing the Goku Uniforms researched by the Sewing Club.

In at least one occasion, experiments have been conducted by the Sewing Club, having a No-Star student wear a prototype Five-Star Goku Uniform. However, this backfired causing the student to become a berserking, muscular, hulk like monster. Hōka Inumuta was the only one able to restrain him. This demonstrates that only certain people have greater control over Life Fiber based clothing. Ryūko, Satsuki Kiryūin, and Ragyō are such people being able to wear and control Kamuis.

Banshi
The Banshi, or Nexus Thread, is a vital Life Fiber present in every piece of clothing made with Life Fibers. It is what holds them together, since it is, according to Shirō Iori, imbued with the will to 'cover'. It is protected by several layers of Life Fibers, making it nearly impossible to be located or damaged. If it is severed or removed, the garment is destroyed.

Most Life Fiber garments have one Banshi, but Senketsu was shown to have multiple threads that must all be removed to destroy him. It is unclear if this is a natural trait of Kamui, a unique element of Isshin Matoi's design, or a consequence of Senketsu's ability to absorb the Life Fibers of destroyed Goku Uniforms (which includes their Banshi).

COVERS
COVERS (カバーズ) are Life Fiber entities that are responsible for the dissemination of Life Fibers throughout the world. The name "Revocs" is an anagram of their name. COVERS can be roughly separated into three groups: Cloth-type COVERS, Humanoid COVERS, and Combat Enhanced COVERS. According to Ragyō, the intent of the COVERS is to "bind the heavens, the earth and mankind, covering all."

Cloth-type COVERS
Cloth-type COVERS take the shape of flat, white business suits with a red bowtie. They can move and fight autonomously as long as they stay in contact with the Original Life Fiber, usually by one or two Life Fibers that connect them to their source.

Humanoid COVERS
Humanoid COVERS are Cloth-type COVERS that are capable of absorbing energy directly from humans, allowing them to act independently of the Original Life Fiber. They assume the appearance of a two-piece suit.

Combat Enhanced COVERS
When a Humanoid COVER absorbs a human being as an energy source, it becomes a Combat Enhanced COVER that specialises in combat and can operate independently from the Original Life Fiber. In this form, the COVER gains a more substantial, muscular appearance, with their "bowtie" enlarging into eye-like growths and a necktie-shaped hole appearing in their chests that bears the emaciated face of its absorbee. Once the human inside is removed, their movement ceases, and eventually break down into threads of Life Fiber.

Lifeforms
Although usually viewed clothing, it is possible through unknown scientific procedures to fuse Life Fibers directly to a human organism in order to create a hybrid Human/Life Fiber life form. Such fused humans are always inhumanly strong and extremely hard to kill, because of their inner Life Fibers' durability lets it regenerate from most damage (unless inflicted in a scissoring motion). There appear to be only two such human beings on the planet: Ryūko Matoi, who was experimented when she was still an infant and believed to be dead, and Ragyō Kiryūin, who has seven star-like scars on her back indicating the location where she was experimented.

It is also possible to create artificial humans by using the primordial Life Fiber as an artificial womb. Those can physically resemble a regular human in every way and even behave as such. They are endowed with the same supernatural strength and durability hybrid Human/Life Fiber display, though possibly to a greater extent. On the flip side, they cannot receive any additional effects from wearing Kamuis or any other Life Fiber-based clothing. Nui Harime is the only one known to be artificially created. It is not known exactly what is the concentration of fibers in her body, but she could potentially consist of 100% Life Fibers.

Life Fibers can also be used for cloning. Rei Hōōmaru made clones of Satsuki Kiryūin and the Elite Four during her capturing of Honnōji Academy in it's "First Graduation Ceremony".

Trivia

 * The concept of living, parasitic clothing/armor is also found in the Spawn comic series. Al Simmons has a symbiotic relationship with K7-Leetha, a living suit that is actually a neural parasite from Hell made of necroplasm.
 * This concept is also similar to the Symbiotes, a race of amorphous extraterrestrial parasites which appear in the Marvel Comics shared universe, the most famous of these are Venom, Carnage, Toxin and Anti-Venom. The Symbiotes envelop their hosts like costumes, creating a parasitic bond through which the host's mind can be influenced.
 * It is revealed in Episode 23, that if either a Life Fibers infused being or a Life Fibers article of clothing gets its both sides cut by a "Anti-Life Fibers" Weapon, it can prevent its regeneration effect.