A Decoy Detonator is a small, discreet magical object designed to create a diversion. In its inert state, it is described as looking like a “black horn-type object.” It is small enough to be surreptitiously dropped from a person's hand or bag without being noticed. Once activated, the device moves of its own accord, adding to its effectiveness as a distraction.
The primary function of a Decoy Detonator is to create a significant and sudden diversion, allowing the user to move or act without being observed. The device is activated simply by being dropped. Upon activation, it scuttles away from the user, often heading towards a populated area or a place where its detonation will cause maximum disruption. After a short period of movement, the Decoy Detonator explodes with a loud bang and releases a large quantity of thick, pungent, black smoke. The combination of autonomous movement, a startling noise, and a visual smokescreen is highly effective at drawing the attention of anyone in the vicinity.
The Decoy Detonator was invented by Fred Weasley and George Weasley as a product for their joke shop, Weasleys' Wizard Wheezes. It was part of their successful line of magical prank and utility items developed during their time at Hogwarts and perfected after they opened their shop at Number 93, Diagon Alley. By the summer of 1996, Decoy Detonators were available for purchase alongside other popular items like Peruvian Instant Darkness Powder and U-No-Poo.