As implied by its name, the Cacophonic Conch closely resembles a real-life musical instrument conch. It is very long, with long pointy spikes on the outer surface and is colored dark purple. Also, its opening glows red.
When blown into, the Cacophonic Conch glows red and gives off a low-pitched sound, which allows the user to inhibit the powers of nearby Zeti, including their ability to manipulate magnetic fields. However, the effect of the Cacophonic Conch is very excruciating to Zeti, causing them great pain when hearing its sounds.
Prior to the events of Sonic Lost World, Dr. Eggman somehow obtained a Cacophonic Conch. With it, he was able to force the Deadly Six into serving him.
When Eggman chided the Deadly Six for collecting "underwhelming" Animals, Zavok spoke up against him. In response, Eggman used the Cacophonic Conch to inflict pain on the Deadly Six as punishment. When later meeting the Deadly Six in Desert Ruins, Eggman expressed his disappointment for their failures despite his effort to help them and blew into the Cacophonic Conch, inflicting the Deadly Six with pain again.
However, Sonic the Hedgehog and Miles "Tails" Prower arrived on the scene, with the hedgehog suspecting the shell was trouble. Ignoring Tails' warnings, Sonic knocked the conch out of the doctor's hands and into the horizon, never to be seen again. This was a terrible mistake, however, as the Deadly Six rebelled and took control of several Badniks before assaulting everyone present.
After the Deadly Six were dealt with, Eggman vowed to find another Cacophonic Conch to bring the Deadly Six under his control again.