This Miraculous is being used for evil purposes — specifically, creating supervillains who attempt to steal Ladybug's and Cat Noir's Miraculouses.
When not transformed, the brooch is oval-shaped and its front is purple. It opens up like a locket, in which an image can be placed. The edges of the brooch and the back of the front part are gray metal, some of it branching out on the outer area of the front of the brooch. When Nooroo inhabits the Miraculous, it becomes a dark purple button, with four light pink strands of fabric coming out from it, making it resemble a butterfly or moth.
The Moth Miraculous grants its wielder the ability to sense positive or negative emotions in order to precisely pinpoint a targeted person's identity. The wielder can energize a butterfly, which turns it black and into an akuma, to be sent to possess an object of the person. Then, the Moth Miraculous holder is able to communicate with the person to offer him or her powers. Once they accept, they transform into super beings. In addition, the wielder can telepathically connect to the possessed person to talk with them. If the akumatized person is using their powers wrongly or not the way the holder wants them to, the holder can cause pain to the akumatized person by controlling the person's body to a certain extent or take away their powers.
In "The Collector", it is revealed that a Moth Miraculous holder can akumatize themselves; to do it, however, they need to first create an akuma and then give up the possession of their Miraculous.
However, these powers do have their limitations. Hawk Moth appears to only be able to make one akumatized villain at a time, and it seems that he must wait for some amount of time between creating villains.