Gabriel Agreste reveals that the Miraculous was damaged under unknown circumstances, however, at the end of Miracle Queen, Gabriel was able to repair the Miraculous with the aid of the tablet he had stolen from Master Fu, which contained a translated version of the spellbook.
In its camouflaged form, the brooch looks like a peacock with the shape of a peacock's body and head at the bottom center and with nine light sea-green tail feathers coming out from it. It has a gold pearl-like gem on each tail feather segment and a blue gem at the base, serving as the body of the peacock.
When charged, the brooch changes from nine feather segments to five. Its main color is dark blue, while the crystals on the top of each segment are pink. The lower part of the Miraculous also changes from the body of a peacock into a single teardrop.
As seen in "Ladybug", the actual damage to the Peacock Miraculous itself includes visible cracks on the back of the Miraculous.
The Peacock Miraculous grants its wielder superhuman characteristics of speed, endurance, and strength.
Its special power allows the user to manifest a Sentimonster, a monstrous creature manifested from a person's emotions. This is achieved by turning a feather into an amok and sending it to inhabit an object belonging to the recipient. The Sentimonster will obey whoever possesses its amok. The wielder of the Peacock Miraculous has the power to revoke the amok, destroying the Sentimonster and purifying the charged feather.
The wielder can also form a telepathic connection between themself and their target. They can also sense where an amok is.
The wielder can also use the power on themselves, namely by charging an amok and placing it in an object the wielder possesses. They can then create a Sentimonster that is completely loyal to them, so long as they possess the amok.
If the amokized target betrays the owner of the Miraculous, they can simply snap their fingers and it will disappear, as seen in "Ladybug".
Peacocks symbolize integrity, vision, and vibrancy.
As seen in "The Collector", the Miraculous spellbook has a depiction of the Peacock Miraculous that is blue and has five tail feathers. However, in "Mayura", the Peacock Miraculous uses the five-feathered design when inhabited by Duusu and the nine-feathered design when in its camouflaged mode.
As noted during an event with the writers, it was "weird" that Plagg didn't recognize it when he and Adrien looked inside the safe in "Volpina".
It has been confirmed that the jewel stored in the safe at that time wasn't the real Peacock Miraculous and is merely a copy created by Gabriel. However, the Peacock Miraculous shown in "Mayura" is clearly the real Miraculous, shown by it being in its charged state, which is activated by having a kwami in its Miraculous.
According to Gabriel Agreste, the Peacock Miraculous is currently "damaged", which results in it causing an adverse effect upon its holder when being used. This is demonstrated by Nathalie's coughing and fatigue as a result of using it.
In "Reflekdoll", the Peacock Miraculous malfunctions between its camouflage and charged state when Nathalie activates it before her transformation.
In "Ladybug", cracks can be seen on the back of the Miraculous.
As seen in the episode "Miracle Queen", the Peacock Miraculous was fixed by Gabriel Agreste using the deciphered spellbook on Master Fu's tablet.
The Peacock and Butterfly Miraculouses have rather similar powers, including charging small things with magic to infect objects of specific people and telepathic communication with them.
Interestingly, both Miraculouses take the form of brooches, which may cast light on the fact that they have such similar powers.
Coincidentally, both are currently kept by Gabriel Agreste.
They are also both currently used for evil purposes.
However, the Butterfly Miraculous's power of akumatization cannot be used on the wielder (unless they renounce it), unlike the Peacock.
Like the Ladybug and Cat Miraculouses, the legacy of the Peacock Miraculous dates back to Ancient China and is over 5000 years old.
It's likely that the Peacock Miraculous was damaged after Master Fu lost it, as he was perfectly fine when he used it to create the Dormant Sentimonster, but when Emilie used after Master Fu lost it, she became ill.
Exactly how the Peacock Miraculous was damaged whilst the Butterfly was not is unclear; it is possible that it was more exposed to the elements or closer to the lava vent that the sentimonster fell into than the Butterfly was and the extreme cold/heat damaged it.