Miraculouses are magical jewels. Worn as jewelry, they have the ability to change their wearers, with the help of kwamis, into animal-themed, super-powered beings.
As explained by Master Wang Fu, Wayzz, and Tikki in the comic story "The Trash Krakken Part 1", kwamis have existed since the beginning of time. Being "abstract" creatures, each kwami formed whenever a new idea, concept, or emotion was formed in the universe, like creation, mathematics, and love. However, tangible creatures like humans could not see or sense kwamis, so the kwamis could only roam the universe without communicating with them.
Thousands of years ago, a mage successfully helped kwamis interact with humans by creating magic jewels, which were called Miraculouses. Because of the kwamis inhabiting them, the Miraculouses bestowed amazing power on their wearers. There are two Miraculouses that are more powerful than the rest: the Ladybug Miraculous, having the power of creation from the first kwami in existence, Tikki; and the Cat Miraculous, having the power of destruction from Plagg. In "Ladybug & Cat Noir (Origins - Part 1)", Nooroo states that legend says when the Ladybug Miraculous and Cat Miraculous are worn together, their user will gain god-like powers. At some point in time, a lot of information about the Miraculouses and their powers was written down in code into a book, with very few knowing how to decipher the code. A jewelry box was also created at an unknown time to store the inactive Miraculouses.
To protect and distribute Miraculouses, the Order of the Guardians was formed and existed for many years. Throughout its existence, guardians trained younger generations to keep a watchful eye over the Miraculouses and the spellbook, which were placed in the Guardians' temple. The Order fell apart more than a hundred years ago because of a mistake made by Fu, a young trainee at the time. The temple was destroyed, and the Moth Miraculous, Peacock Miraculous, and spellbook were lost, but Fu took the box with him.
According to Nooroo, the Miraculouses, meant for good purposes, have been used by heroes throughout history. However, in the wrong hands, Miraculouses may be used for evil.
Usually, a Miraculous is assigned to an appropriate user with good intentions by a guardian, a human tasked with watching over the Miraculouses and keeping them in a safe place when not being used. While there is a chance of giving a Miraculous to an unworthy candidate, as Wang Fu has done once with an unknown individual, the system prevents many unfit people from getting Miraculouses easily. The guardian takes back and stores the Miraculous when it is discarded or returned to him. Unfortunately, there have been cases where Miraculouses are lost, even potentially forever, and the guardian is unable to retrieve them, like when the Moth Miraculous was presumed to be lost forever by Wang. Miraculouses can be kept by their chosen users for many years as long as they are being used and the holders' bodies are capable.
There are ways to get Miraculouses outside of being chosen by the Great Guardian. People can find Miraculouses if they have been lost and are unable to be stored properly. For example, Hawk Moth got the Moth Miraculous by finding it, also making it easy for him to utilize it for evil without Wang Fu's interference or knowledge of his secret identity. Previous Miraculous holders can also give their Miraculous to someone else if they don't know a guardian or the guardian can't intervene first. After believing she shouldn't be the Ladybug Miraculous holder in "Stoneheart", Marinette sneaks the Ladybug Miraculous into Alya's bag in hopes that Alya will find it and take over as Ladybug, although Marinette later decides to continue as Ladybug and retrieves it before this can happen.
Another option for getting a Miraculous is stealing a Miraculous and/or removing it from its user. There are different kinds of motivations for taking another user's Miraculous. One motivation is Hawk Moth's intention to get the Ladybug Miraculous and Cat Miraculous to access their absolute power when combined. On the opposite side, if a Miraculous is being used by a villainous person, it is the Great Guardian's task to find out who the Miraculous holder is and take the Miraculous away from them. If needed, the Great Guardian will get help from other Miraculous holders or choose new Miraculous holders in order to stop the villain, as when Marinette and Adrien receive Miraculouses from Wang Fu to defeat Hawk Moth. Along with being vulnerable to being stolen if they aren't being worn, Miraculouses can be forced off the user by someone else when they are being worn, whether or not they are transformed. Despite being possible, it's less common to be able to steal the Miraculous when the holder is not transformed unless the taker knows what the Miraculous looks like when in its dormant form.
Or when under permission of the Great Guardian a current Miraculous holder can temporarily give a Miraculous, to someone else as long as the temporary wielder returns it when the mission is over. Seen with Alya in "Sapotis", when Ladybug chose her to wield the Fox Miraculous in order to help them.
Not all Miraculouses in other people's possession are worn and wielded by them. Master Wang Fu keeps unused Miraculouses in the jewelry box in order to keep them protected and have them available for future chosen users in required situations. In a secret safe, Gabriel Agreste stores the Peacock Miraculous, a detail that goes unnoticed by Adrien and Plagg in "Volpina". At the same time, Miraculous holders who wear Miraculouses may never or rarely transform with them. Because of his age, Wang Fu struggles when he attempts to transform in "Ladybug & Cat Noir", hurting his back in the process. Nonetheless, Wang keeps and wears the Turtle Miraculous, often discussing matters with Wayzz and benefiting from Wayzz's assistance.
A Miraculous, when worn and inhabited by a kwami, transforms the wearer into a costumed guise based on its animal theme and what they wanted deep down. It also grants the wearer enhanced abilities, like strength and agility, a weapon, and a unique superpower. Some of the Miraculouses' powers follow their theme, like the Ladybug Miraculous, with the power of creation, having the superpower Lucky Charm. The kinds of powers a Miraculous has aren't limited to the theme, though. The transformation lasts until the superpower is used, leaving the wearer about five minutes until they revert back to normal. Before the wearer can transform again, the kwami needs to recharge by eating food.
A person can wear more than one Miraculous and use them both at the same time. However, it is unknown what happens to the user when they transform, like if they take on aspects from one or both Miraculouses or if they gain more power from both Miraculouses being combined.
To deactivate a Miraculous, the person must dispose of their Miraculous intentionally, either "renouncing" the Miraculous' kwami or expressing the desire to no longer use it. Once done, the kwami goes back into the Miraculous, only awakened when someone opens the Miraculous from a small box from a guardian, or they put on the Miraculous. However, kwamis do not return to their Miraculous in dormant form if the holder involuntarily gets rid of it, as seen in "Lady Wifi" when Cat Noir's ring falls off and gets lost.
Jewelry that turns the wearer, with help from the dog kwami, into a dog-themed hero.
The Ladybug Miraculous and Cat Miraculous are set opposite each other in a yin-yang (tajitu) section in the Miraculous box. The Cat Miraculous is placed in yang, and the Ladybug Miraculous is placed in yin. The other Miraculouses are arranged around them in a similar fashion to the five elements in Wu Xing (albeit which one corresponds to each is not clear).
More than one Miraculous can be the same type of jewelry, such as the Moth Miraculous and Peacock Miraculous both being brooches.
There are only seven known Miraculouses so far, which are stored on the top level of Wang Fu's chest, but Thomas Astruc explained that it's a bit more complicated than that, with more information being discovered about them throughout the three seasons of the series.
In the animatic of the theme song, the chest box has many Miraculouses that are not used in the final version, including what appears to be an Eagle Miraculous, Snake Miraculous, Bear Miraculous, Lion Miraculous, Chicken Miraculous, and Bull Miraculous.
Using the same setup in the animatic for "Ladybug & Cat Noir", the Miraculous box has most of the same Miraculouses, but the Moth Miraculous is replaced with Fish Miraculous earrings.
According to what Wang Fu says in "Princess Fragrance", the Miraculouses might be connected to ancient China.
The Miraculouses on the lower levels of the box all correspond with the Chinese zodiac.
The official Miraculous Ladybug Tumblr blog noted that the TV series, comic books, and web series will show the history of the Miraculouses.
Miraculouses can be negatively impacted if the kwami enters it with another object, lessening the wearer's power, which Plagg explains to Adrien in "Rogercop" when he gets Chloé's bracelet stuck on his head.
As revealed by Sébastien Thibaudeau in a press release video, in the future, Marinette will "find herself giving Miraculouses."
Also, at some point, a female character will give back a Miraculous to Ladybug. The character and the Miraculous currently being unknown.
It was later revealed in "Sapotis" that the character Ladybug gave a Miraculous to and was later returned to her was Alya, who received the Fox Miraculous.
In "Frightningale" Plagg mentions that Chat Noir's costume is what Adrien really wants deep down.
This would mean that the appearance that the Miraculous holders assume when they activate their transformations, reflects their tastes and desires.