Magicule

Magicules (魔素) or Magical Particles are a particular type of matter heavily influenced the minds of living beings and able to take on many different properties depending on the situation. They are both the building blocks of and sustenance for Monsters.

Properties
Magicules are made up of Spiritrons or Spirit Particles, the spiritual equivalent to neutrons bearing no attributes. As matter composed of spiritrons, magicules naturally have spiritual properties. They are naked to the human eye and despite having mass, do not normally interact with most types of physical matter and energy, although they are capable of doing so. They act as a sort of radiation and can be found inside of materials as well as in the atmosphere.

Magicules are a particle highly susceptible to the thoughts and emotions of living beings. At the most basic level this can be utilized to fill magicules with one's intent and then flinging them at a target, achieving a sort of telepathic communication. More advanced practitioners can fill magicules with complex images of phenomena by imagining the laws behind them, changing the form of the magicules to match that of the mental image, and performing what is known as Elemental Magic.

Many spiritual lifeforms interact with the material world by creating temporary bodies made out of magicules called a Magic Body (魔体), and thus physical attacks do not have any "proper" effect on them. One would need Magic, Skills, Battlewill, or Weapons that can affect spiritual matter to deal proper damage. An example of this would be Eren attacking Ifrit's salamanders with her Icicle Lance.

Effects
Magicules act similar to radiation, and just like radiation, there is a safe "limit" of it that beings can handle before experiencing adverse side effects and eventually death. Regular untrained Humans have a low amount of magicules within their bodies and possess a similarly low resistance to magicule exposure, while their Demi-Human cousins almost all bear much higher tolerances, leading to much jealousy and discrimination over the years. Monsters on the other hand, are beings composed almost entirely of magicules and need them as sustenance to maintain their existence, although even they have an upper limit to how much they can handle.

In areas with a high enough concentration of magicules, they can coalesce together and form a monster. The level of the resulting monster is dependent on the magicule concentration from which they were born and by being exposed to an even higher magicule concentration over a long enough period of time, it is possible for them to evolve.

Rarely, when a living thing is exposed to too many magicules, instead of dying it might adapt to the magicule concentration and be reborn as a monster. Even Elementals are susceptible to magicules and coming into contact with too many magicules might corrupt them, turning them into monsters. Even the Elemental Queen is no exception to that.

Inanimate Substances
Although magicules are most well known for turning living things into monsters, they are also capable of affecting inanimate objects as well. In most cases, only in regions with high magicule concentrations, such as; the Sealed Cave and Rimuru's Stomach, inorganic and inanimate substances can absorb magicules to become a magical substance, such as magisteel or magistone.

In such cases, the substance remains an inanimate object but due to being partially composed of magicules, it is capable of reshaping itself into a form influenced by the thoughts of others as well as bearing magical properties. It is also possible for the material to become a monster, being reborn as a Golem.

Skills
When one's power and desire come into alignment it is acknowledged by the world itself and skills are the result. A sentient beings magicules are consumed and transformed into a skill, with them being able to call on that skill at any time to automatically perform a specific action or phenomenon, most commonly Magic. These skills can be born out of acknowledgment for mastering an Art or by one's desires becoming so strong that the magicules react to it and take a form that matches. In any case, obtaining a skill permanently decreases one’s magicule capacity, hence why humans and weaker individuals whose capacity was low to begin with don’t tend to possess many.

Trivia

 * Magicules are analogous to "Mana," or "Magic Points," or "MP" in games and other shows.
 * The term "Magicule"; is derived from "Magic" and "Molecule"; it should be noted that the term's Kanji itself; is referring to a magical/demonic Chemical Element or Atom instead, so describing it as a Molecule might be considered a mistranslation by the official translators. In addition, the Kanji being translated as "Magical" could alternatively be interpreted as "Demonic" as well; which is why Magicules are usually associated with Monsters.

pt-br:Magícula Магическая Энергия