The Miraculous has the power of illusion. The necklace is temporarily owned by Alya in "Sapotis", who uses it to turn into Rena Rouge.
The Fox Miraculous is a necklace. 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 orange to white. 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.
The wielder's superpower is Mirage, where can play the flute and create one illusion that they desire. So long as the superpower is not used the wielder can sustain the transformation indefinitely but once doing so, they only have about five minutes until they transform back.
List of owners
Ancient Chinese Fox Miraculous holder
A Fox Miraculous holder displayed in the Miraculous book.
Alya Césaire (spoiler)
A teenage girl in France and a temporary Fox Miraculous holder. She gets it to help Ladybug and Cat Noir in "Sapotis".
The last known remaining guardian. He is currently storing the Fox Miraculous in the jewelry box.
Order of the Guardians
The guardians of the Miraculouses. The order protected the Fox Miraculous until it fell apart.
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 it is unsure if this is the Fox Miraculous' real power.
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 it's disguise mode except that it's active mode has four golden metal lines dividing the pendant into five sections.