Abyssal Signet

Abyssal Signet is used to increase reputation with the Cenarion Circle.

Source
Abyssal Signet drops off the Abyssal Dukes in Silithus.

As a quest objective

 * Twilight Ring of Lordship
 * Abyssal Signets (quest)
 * Lords of the Council
 * Signet of the Dukes