Nathalie Sancoeur

"They've been keeping you from achieving your dream for way too long. I will go to any length to end the reign of Ladybug and Cat Noir."

- Nathalie

Nathalie Sancoeur is Gabriel Agreste's assistant who manages his mansion and takes care of his son Adrien.

In "Catalyst", which is part of the "Heroes' Day" special, she is akumatized by Hawk Moth into Catalyst, a power-enhancing supervillain.

In "Mayura", in order to help Hawk Moth escape from the French Miraculous superhero team, Nathalie uses the Peacock Miraculous and, as the Miraculous is inhabited by Duusu, she becomes Mayura, a peacock-themed supervillain who helps Hawk Moth by creating allies for akumatized villains and she is said to appear as Hawk Moth's "boss" in Season 3.

Physical appearance
Nathalie stands at an average adult height with black hair that is pulled back into a bun with the hair on the left side of her head that is dyed a dark pink or red color, a piece of hair hanging over her face and dull blue eyes.

Civilian attire
Nathalie has glasses with black and red striped frames and she wears periwinkle eye shadow. She wears a red turtleneck sweater, a black dress jacket, black pants and black medium-heel shoes. She also has round creamy-white earrings.

As Mayura
Mayura's eyes have pink irises and scleras that are pink which fade into dark indigo, and there is black liner around her eyes, resembling glasses. Her skin is a light indigo and her hair is dark blue, and part of it curls up underneath her left eye. She wears a peacock-feather-like cocktail hat, which is blue and tear-shaped with a light pink mark in the center and a light blue, translucent veil over her right eye. She wears a blue dress with a fuzzy black collar and sleeves that end in a point on the back of her hand. The dress appears to have a set hexagonal texture, as well as a Peacock Miraculous in the center. The bottom of the dress has a front-slit skirt, and the end of the skirt has rounded points with dark blue, light-pink-centered spots, resembling a peacock's tail feathers. The rounded points are edged with translucent light blue material. Underneath the dress, she has translucent indigo tights that are opaque from the knees down, making the opaque section resemble high-heeled boots. She holds a blue hand fan, which is similar in design to the end of her skirt, and a peacock-feather-like object in her other hand.

As Catalyst
Catalyst has periwinkle skin. Over her head, while leaving her mouth exposed, she wears a black helmet with a red visor with black edges and a red spike pointing towards the back of her head. Catalyst also wears a black dress suit with stiff shoulders, including a dark red front and swan neck collar that features a red downward-arrow-shaped section in the center. The sleeves cover her entire arms, with the tips of her fingers fading into red. Also, Catalyst has pocket-like ridges on each side of her hips, and her pant legs come down to her feet, having red high-heels, soles, and tips.

Personality
Nathalie is a serious and formal woman who works very diligently as Gabriel Agreste's assistant. She has a cold and distant demeanor as she doesn't openly show her emotions around others most of the time. Smart and sensible, Nathalie is able to reason with Gabriel and Adrien whenever they are acting inconsiderately or emotionally, sometimes in relation to each other. While not warm, she can be cordial and polite. However, in situations where she is dealing with Gabriel, she becomes nervous, being afraid to disappoint him. Her desire to be on his good side leads her to unfair actions, such as giving Adrien a birthday gift and claiming it is from Gabriel when it is actually from Marinette in "The Bubbler". She cares for Adrien, although she doesn't usually openly show it, as she requests to Gabriel that his son go to school on his behalf while she would handle his schedule, and she desires what is best for the Agreste family.

However, her concern is limited to the Agreste family only, and she doesn't seem to care about the other Parisians' well-being. In fact, she obeys Gabriel's orders with fierce loyalty no matter how morally wrong they are and even helps him with his plans, which is seen in "Catalyst (Heroes' Day - Part 1)" and "Mayura (Heroes' Day - Part 2)" as she takes sadistic joy in fooling the heroes into thinking they can win all the while. Even though Nathalie has a cool and calm demeanor, she can lose her temper on occasion and would disregard any detrimental consequences as a result, as seen in "Mayura", when she was frustrated by the fact that her boss was failing, and even went as far as letting herself be harmed by the power of the damaged Peacock Miraculous in her transformation.

As a civilian
Nathalie is an effective assistant, being able to take care of Gabriel’s needs and organize Adrien’s schedule.

As Mayura
Mayura has enhanced physical characteristics: speed, strength, and agility. She shares similar abilities with Hawk Moth as she is able to infuse a feather plucked from her hand fan with her power, transforming it into an Amok, and send it out to possess an object owned by a chosen target, with whom she can communicate telepathically. This action will then give an emotion from her target a physical form of that person's choosing, to act as the target's ally until recalled by Mayura via a snap of her fingers, which destroys it. While she is communicating, a blue curved peacock mask appears in front of her and her target's faces.

As Catalyst
Catalyst has the power to multiply/enhance/increase someone's powers; she does this by infusing scarlet energy into an object belonging to her target, similar to an akumatized object. When affected, the person gains a red-colored outfit. In Hawk Moth's case, with this power enhancement, he became Scarlet Moth, allowing him to akumatize multiple butterflies and transform multiple people at once. She can also communicate with the person she enhanced, during which a red sharp-edged butterfly mask appears in front of both of their faces, similar to Hawk Moth.

Gabriel Agreste/Hawk Moth
Nathalie works professionally as Gabriel's assistant. She makes sure to take care of all of his requests and looks after his son, Adrien. Occasionally, she tends to get nervous when dealing with him, such as when she forgot to buy a gift for Adrien on his behalf, leading her to lie and tell Adrien that Marinette's gift was actually from his father. Although wary of him becoming disappointed with her, she is willing to stand up to him for Adrien's sake, as when she voiced her displeasure with him for being too distracted by his missing wife to see his own son's misery during "Santa Claws".

In "The Collector", it is revealed that Nathalie is aware that Gabriel is Hawk Moth. Furthermore, "Queen Wasp" indicates that she has deep feelings for Gabriel, being relieved when he decides to stop being Hawk Moth but devastated when he changes his mind because he loves Emilie too much. Her loyalty is so strong that in "Catalyst", she helps with his plan for taking Ladybug's and Cat Noir’s Miraculouses by allowing him to akumatize her, and in "Mayura", she even risks herself by using the damaged Peacock Miraculous to transform into the titular villain in order to help Gabriel after he, as Hawk Moth, gets de-transformed back into his normal villain form.

Adrien Agreste/Cat Noir
Nathalie is usually serious around Adrien, not being very warm or close to him. Despite this, she does care for him, which she shows when she requests to Gabriel that Adrien be allowed to go to school after seeing how much he wanted to attend. She also shows that she cares for Adrien in "Santa Claws" when she sees how sad he is about his father not celebrating Christmas, and asks Gabriel to spend time with his son. She even softly smiles at Adrien's joy at his friends being allowed into the mansion on Christmas.

Nathalie is unaware that Adrien is Cat Noir. However, she despises the hero and wants to help Gabriel take his Miraculous from him, even telling Hawk Moth that she'll go to any lengths to end his reign.

Marinette Dupain-Cheng/Ladybug
Nathalie has seldom encountered Marinette personally, only seeing her in person during the derby hat competition in "Mr. Pigeon" and briefly interacting with her in "Style Queen". However, on Adrien's birthday in "The Bubbler", she treats Marinette formally when on a speaker and disregards her by claiming to Adrien that Marinette's gift was from Gabriel.

Nathalie is unaware that Marinette is Ladybug. However, she despises the hero and wishes to help Gabriel take her Miraculous, even telling Hawk Moth that she'll go to any lengths to end her reign.

{{HideSpoiler|

Chloé Bourgeois/Queen Bee
Like most Parisian citizens, Nathalie is aware that Chloé is Queen Bee. Though she does express a little bit of doubt about it, Nathalie willingly helps Gabriel in his plot to bring Chloé over to his side. As Mayura, while battling her, she tries to persuade Chloé into joining her and Hawk Moth by saying that if she does, she can be Queen Bee whenever she likes, though Chloé refuses.}}

Trivia

 * The name Nathalie means "Christmas Day/Christmas".
 * Nathalie's surname Sancoeur ("sans cœur") means "heartless" or "without a heart" in French.
 * Nathalie appears to be left-handed as she does most things with her left hand like holding a stylus in her left hand during "Ladybug and Cat Noir (Origins - Part 1)".
 * Nathalie's akumatized form, Catalyst, was first revealed in a promotional video for Season 2 from TFOU.
 * Catalyst also shares a resemblance with the Collector's design as they both have purplish skin, red glass over their eyes and black dress suits with stiff shoulders.
 * Nathalie is the first character to explicitly be willingly akumatized (aside from Gabriel Agreste akumatizing himself in "The Collector"), although Lila Rossi's smirk after her de-evilization implies she may have also been willing to serve his scheme.
 * Catalyst is so far the only akumatized villain not to be defeated by the French Miraculous superhero team and the only one they are not aware of.
 * Following Alya Césaire, Nino Lahiffe, and Chloé Bourgeois, Nathalie is the fourth person to become a Miraculous holder and akumatized villain, excluding Gabriel, who akumatized himself.
 * Catalyst is also the first akumatized villain to enter Hawk Moth's lair, aside from The Collector.
 * She is also the first akumatized villain who didn't fight Ladybug and Cat Noir.
 * The name Mayura in Sanskrit means peacock, one of the sacred birds in Hindu mythology. It is also a contemporary Hindu name used in many parts of India.
 * While the villain is female, Mayura is specifically the term for males while Mayuri is the term for females.
 * Mayura was revealed at the Miraculous panel at New York Comic Con 2016 under the name "Le Paon" (French for "The Peacock").
 * Earlier, at a panel at San Diego Comic Con, Thomas Astruc pointed to an image of her in the sneak peek collage image, commenting that she will be a new recurring supervillain that will be Hawk Moth's ally.
 * In a video interview held on August 25, Jeremy Zag mentioned that the new main villain will make Hawk Moth appear like "a baby" in comparison.
 * Her final name was revealed at a TF1 press conference advertising the upcoming Season 3.
 * Mayura's civilian identity was revealed by the end of Season 2.
 * There were also clues about her in the opening theme song for the season.
 * She’s the second Miraculous holder to use their power for evil after Gabriel Agreste.
 * She's also the first Miraculous holder whose skin tone changes color when she transforms.

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