This lore can be found on the planet Dromund Kaas.
Fear is a powerful weapon, and those who wield it can rule the galaxy. The Phobis devices were constructed for just that purpose. Brimming with dark energy, their mere presence was enough to spark crippling horror in the bravest of minds. Many Sith who meditated on the devices were driven mad by their attempt. Only the lost Sith Dread Masters successfully harnessed and perfected the Phobis devices’ frightening power. Three known Phobis devices exist, and the Emperor sealed one of them–the Core–within his Dark Temple. Although its dormant components have been scavenged, the Phobis Core remains active and will likely spread fear and hysteria for generations to come.