The Fox Miraculous is a necklace that, whenever Trixx inhabits it, transforms the wearer into a fox-themed superhero, who possesses the power of illusion. The necklace was temporarily owned by Alya Césaire in "Sapotis", who uses it to turn into Rena Rouge.
It appears that the necklace is given back to her on other occasions when the need arises.
It has a golden chain with a white-tipped orange fox tail pendant attached to it. When inhabited by Trixx, it gains four golden metal lines protruding from the border, dividing the pendant into five sections, and the sections change in color, from top to bottom, from orange to white with a gradient effect. When its holder starts running out of power, the top section of the Miraculous turns black, with each following section turning black the closer the holder is to detransforming.
The Fox Miraculous provides its wielder superhuman characteristics of strength, speed, durability and most notably, agility. The Fox Miraculous' special weapon is a reed flute, as illustrated in the Miraculous Spellbook.
Its special superpower is Mirage, which allows the wielder to create one hyper-realistic illusion of their choice when the flute is played. Once played, an orange-white ball of energy appears at the flute's end which the wielder then throws to create the illusion. So long as the superpower is not used the wielder can sustain the transformation indefinitely, however once it is used they only have about five minutes before they transform back.
Foxes are a symbol of cunning, wisdom, and passion.
In the theme song, the Fox Miraculous briefly appears in the Miraculous jewelry box, although it is obscured by the raised middle section of the chest box with the Ladybug Miraculous and Cat Miraculous.
In "Volpina", Lila purchases a necklace with a similar design to support her lie to Adrien that she is a Miraculous holder, and it becomes her akumatized object.
Thomas Astruc reaffirmed that the necklace is from a store on Twitter, acknowledging that the scene where she gets it is very short and easy to miss.
In the Miraculous spellbook, one of the codes on the Fox Miraculous page translates to Volpina, but it's unknown if it's the name of the Fox Miraculous holder depicted or an Easter egg.
When Lila is akumatized, becoming a supervillain based off the ancient Chinese Fox Miraculous holder, she gains the power of illusion, but unlike the true Fox Miraculous, she can create as many illusions as she wants, unlike Mirage which only grants one illusion before starting the countdown of five minutes before detransforming.
As of "Sapotis", it's revealed that the power of illusions is indeed the real Fox Miraculous' power.
At the Anime Expo 2016 panel for the show, it was stated that the wielder of the Fox Miraculous (not an akumatized villian based off of them) "will be potentially a recurring character."
This was confirmed again at the panel at San Diego Comic-Con 2016, along with that the Fox Miraculous and its wielder will appear in Season 2.
Unlike the Ladybug and Cat Miraculouses, the active mode of the Fox Miraculous isn't that different from its disguise mode except that its active mode has four golden metal lines dividing the pendant into five sections.
In the Miraculous spellbook, both are shown in their active modes however the Fox Miraculous is shown in its disguise mode.
The Fox Miraculous is so far the only Miraculous not in constant possession by its holder.