Kwamis are divine beings that are formed whenever a new abstract idea or emotion comes into existence in the universe, such as creation, love, beauty, and mathematics. The very first Kwami ever to come into existence is Tikki, the Kwami of Creation, who came into existence upon the creation of the universe.
All of the Kwamis know each other and journeyed across the universe for eons. However, the Kwamis were spirit-like, and thus couldn't be perceived by regular, tangible lifeforms, such as humans, and were therefore unable to interact with them.
Thousands of years ago, a Chinese mage figured out how to create special magical jewels, the Miraculouses. These jewels allowed the Kwamis to manifest in physical form, finally allowing them to communicate with mortal lifeforms, though the physical form can only be manifested when a Kwamis respective Miraculous is in the possession of an owner. In return for the privilege of having the ability to be perceived by mortals, the Kwamis were able to grant superpowers to their Miraculous owners.
From that point on, Kwamis helped the wearers of their Miraculouses transform into heroes and achieve good all around the world. There were instances where they became stuck with villainous owners and were forced to help them with their diabolical schemes due to being bound to their miraculous owner's every command, such as Nooroo and Duusu currently in the series. Some of them have made long-lasting and meaningful bonds of friendship with their owners and to commemorate that special bond, they'd give their owner a jewel, known as a Kwagatama.
A long time ago (long enough for some Kwamis to forget), a magical spell was cast upon them. They are physically incapable of speaking their owners' names to each other or any Miraculous owners other than their own. However, if another Miraculous owner already knows their owner's identity, then the Kwami can speak their owner's name freely.
In "Sandboy", it is revealed that active Kwamis collect items from the outside world inside the Chinese Miracle Box to give as presents to inactive Kwamis for entertainment.
Just as Miraculous holders were taught about the powers of the jewels, so were the kwamis, such as the Miraculous potions, that allowed them and their owners to change into their elemental forms. However, even though they were curious about how their powers could be modified, they were forbidden by the guardians to know as a precaution in case if they ever fell into evil hands.
Over time, the kwamis also became aware that they could unify their powers as well as the danger that came when one holder fused too many jewels together, as seen in "Miracle Queen", when Stompp, Roaar and the others refused to share their activation commands after seeing Chloe's rude and selfish behavior. They also knew that Chloe could've severely hurt herself, so they refused for her own safety. They also were aware of the Guardian's Code and sometimes like their owners they share meaningful bonds with the guardian's of their boxes.
Sometimes depending on certain situations or emergencies kwamis would often return to the home cities or towns of their previous owners but come under the ownership of new holders like in the case with Tikki.
Generally, kwamis are small, being around 10 centimeters (4 inches) in height, with large heads, big eyes, tails in different sizes, and tiny bodies. They have arms and legs, and though they lack fingers and toes, kwamis are still able to grab things. The animal theme that they display is reflected in their Miraculous; for example, Plagg is black with green eyes and has cat-like ears and a cat-like tail. Fittingly, his Miraculous is the Cat Miraculous.
After consuming certain potions made from the Miraculous spellbook, their appearances will change. If the aqua mode potion is used, the kwami will gain fins and a fishtail. In "ice mode", the kwamis gain crystals on their bodies.
Kwamis are divine beings who can phase through matter, levitate, survive without oxygen, and are also immortal. Despite the Miraculouses granting them physical form, Kwamis don't show up on cameras, photos, videos, and they can't be seen or perceived by artificial intelligences, such as robots and androids, like Aeon.
Even though they are small, Kwamis appear to have a human level of strength. They have displayed the ability to hold and lift things that are larger and/or heavier than themselves. Kwamis can also possess or inhabit objects.
They can also perform a ritual for their Miraculous owners where they create a Kwagatama inside their bodies from the hairs of their past and current owners. They then present the charm to their current bearer for a special occasion, such as a birthday.
Kwamis each have a unique superpower, each power corresponding to the abstract concept that the Kwami embodies.
When a specific command is given, a Kwami will inhabit its Miraculous to give the person wearing it the ability to transform into an animal-themed superhuman and gain a specific power based on the abstract idea or emotion that made the kwami come into existence. They are aware of the actions of the people who use their Miraculous when transformed, but they cannot communicate with their owners during that time. At the same time, the extent they can be aware of what is happening when their Miraculous is used is uncertain: after the battle with Stoneheart, Tikki and Plagg were unaware the Ladybug forgot to capture the Akuma.
When a Miraculous owner transforms, the invoked kwami transforms into pure energy to charge the owner's Miraculous and give them their power, thus, resulting in them in disappearing.
The Miraculous transformation can last indefinitely, unless the Miraculous's special superpower is used, at which point, the wearer has five minutes until they detransform back to their normal form and the kwami leaves the Miraculous, completely out of energy when paired with a younger Miraculous holder. As seen in "Anansi", just summoning the power can drain the kwami's energy. In "Timetagger", just staying transformed takes a toll on them if held for long periods of time. To regain their strength for another transformation, the Kwami needs to refuel by eating food. Any food will work, though some have a preference for specific foods. Plagg is one of these picky Kwamis, as all he ever seems to eat is Camembert cheese and not an ice cream sundae prepared by Adrien's personal chef.
When the Miraculous is worn by an adult owner, the Kwami can maintain the transformation, even after the special power is used, and the power can be used multiple times.
Despite their god-like nature, Kwamis can get sick, as seen when Tikki becomes sick after helping Marinette defeat a villain in the pouring rain. Wang Fu can assist in their recovery and heal them. It's unknown if a Kwami can only get sick while inside a Miraculous or to what extent this could harm them or affect their wielders. However, since it's the kwamis that give their owners their powers and transformations if they transform under these conditions, it's likely that they won't be able to hold it for long let alone give their owners their powers. It's unknown if a damaged Miraculous has any effect on a kwami like in Duusu's case.
As abstract entities, they have been around since before the creation of the Miraculouses, meaning even if their Miraculous is destroyed or erased from the timeline, they will return to their natural state, in which case they cannot be perceived by mortal senses under normal circumstances; they do not cease to exist.
Kwamis can communicate with each other on a Kwami's "cycle" (the Kwami equivalent of a birthday) if they gather in the Miracle Box at a specific time and chant all together. The more kwamis there are, the stronger the connection is, and the more likely it is to work. They also can dispel the connection. If the Kwami being contacted is powering a Miraculous at the time, the other Kwamis will contact the Miraculous' wearer instead.
When Kwamis are powering their owners, they have some level of resistance to an Akumatized villain's attacks, as seen in "Dark Cupid". However, if their owner is attacked by an Akumatized villain's powers and detransform afterward, the effects will transfer to the Kwami, as seen in "Oblivio".
If a holder wears a Miraculous of two kwamis' or more their unification capabilities are activated creating a hybrid Miraculous holder and yet it's unknown if constantly fusing two Miraculouses or more will have lingering or harmful effects for the kwamis.
According to "Origins Part 1" and "Timebreaker", Kwamis are capable of sensing the power of other kwamis and even their own powers when active under certain circumstances like time travel. However, it seems that their range can be limited or they can't sense the powers of another Kwami when they're not active, as Wayzz was unable to sense Duusu when he was activated prior to the months before Nooroo were. As well as sense the aura of other beings including humans done by Liiri in "Miraculous New York".
The Miraculous spellbook contains recipes for potions that can alter a kwami's appearance and form, either by drinking the potion directly or consuming something edible that contains the potion. After the Kwami has ingested a potion, the kwami's Miraculous wielder will get new abilities and appearances in their superhero form, depending on the potion the kwami consumed. These extra powers last for only a single transformation.
The known power-ups are:
Aqua - The kwami's legs are replaced with a fishtail, and their hands are replaced with flippers. It allows the kwami to grant underwater abilities to their holder. The potion's color is green.
Ice - The kwami grows three ice shards somewhere on its body. In some cases some part of the body will be slightly altered, such as Tikki's spot which turns into a hexagon. It allows the kwami to grant ice-related powers to their holder. The potion's color is blue.
Space - It is unknown what a kwami looks like in this form. It allows the kwami to grant space-related powers to their holder. The potion's color is purple.
Inhabits the wearer's Unknown Jewelry for them to transform into a goose-themed superhero.
Tikki is the oldest kwami. As she is the kwami of creation, she has actually existed ever since the creation of the universe.
The concept of the kwamis was created by Bandai. A kwami is a "quantic (small) kami." In Japanese, kami (神) often refers to a god or certain kinds of spirits.
Wilfried Pain noted in a Twitter response that kwamis are "some kind of god" and don't exactly have genders. He also mentioned that the kwamis are supposed to look very cute.
Nonetheless, in "Sandboy", kwamis refer one another (Sass as an example) as brothers or sisters.
According to Thomas Astruc during a Miraculous panel at Ludicomix 2018, some kwamis being inspired by the Chinese zodiac signs is because he wants the world to get to know the elements of Chinese culture.
According to Thomas Astruc, the name of every kwami has to be a short name with double letters in it.Nooroo's name has two doubles.
Kwamis are like Aladdin's genie, having to obey their holder's desires. They aren't genies themselves; however, genies do exist in-universe, according to Plagg in "Ladybug & Cat Noir".
If the Miraculous jewel gets destroyed, the kwami reverts to their spirit form, unable to be seen by living beings.
According to Jeremy Zag, Season 2 would include an episode revealing the origins of the kwamis.
The New York Comic Con 2016 panel additionally noted that there would be Miraculous Secrets webisodes that focus on the kwamis, notably Tikki and Plagg (revealed as "Tikki" and "Plagg"), and that there may be more than one episode in new seasons that centers on them. "Sandboy" is one such episode.
The official Miraculous Ladybug Twitter account noted that while more kwamis would be seen in Season 2, it wouldn't be all of them.
According to Tikki in "Sandboy", a kwami's cycle or birthday is equivalent to several hundred human years.
Plagg used his Cataclysm to make the dinosaurs go extinct, but since this happened before the jewels were made, it means that kwamis are capable of using their powers in their spirit forms.
Even though some kwamis don't have noses, they seem to have a sense of smell; for example, in "Stormy Weather" Plagg said he could "smell Camembert in his sleep."
In "Oblivio", he was seen sniffing Adrien's shirt, smelling the Camembert within.
As the Miraculouses have been used by people across the world throughout history, kwamis are likely able to understand and speak many, if not all, languages to communicate with their holders.
Which is confirmed to be true as Tikki in "Miraculous Shanghai" could fluently speak Chinese and automatically any other language which is essential because they don't know what kind of wielder they'll get.
This also confirms that the phrases used to transform and use their powers can be said in any language.
According to Tikki in "Félix", kwamis live forever, meaning that they are immortal.
In "Feast" since the sentimonster's destruction returned the Guardians and the destroyed Miraculous, it means that not only are there more Miraculouses but, also, more kwamis.
If Plagg's Cataclysm could take out most of Paris, it can be assumed that the other Kwamis have much stronger versions of their Miraculouses' powers. However, it is unknown if their powers could be as catastrophic and uncontrollable without a wielder like Plagg's. It is however said multiple times that a kwami using their powers without a wielder is too dangeros.