The official GemStone IV encyclopedia.
Black coral amulets are objects associated with several Wehnimer's Landing storylines, notably Cross Into Shadows. Note, they are not items which are available to characters in a functional sense.
Hearthstone Doorman's Account
The doorman says, "They were called The Illuminator's Talisman."
The doorman says, "The origins of this device originate from the city of Toullaire, a few decades before it was utterly destroyed in a magical catastrophe, creating the ravaged land known as Ba'Lathon, or the Wizardwaste."
The doorman says, "It is rumored that these devices are created using ash collected from the cloud that hung over Ba'Lathon for months, along with a strange, liquid substance said to be collected from the demonic valence of Shien'tyr. In addition, the user's blood must be sacrificed and infused into the amulet in its original creation. A gem must be used, and may be any color of coral."
The doorman says, "The talisman is always made in pairs. As it can capture the thoughts and voice, and even sights of its user, and remotely duplicate and store them elsewhere."
The doorman says, "These amulets were said to originally be used by the Faendryl, who likely led to humans within Toullaire acquiring the knowledge. Shortly after the Wizardwaste was created, many of these devices were collected and, presumably destroyed. Some still exist, but are forbidden to be used under Turamzzyrian law."