Obsidian Idol

Source
Obsidian Idols are shiny black statuettes that drop from trash mobs in the Ruins of Ahn'Qiraj.

As a quest objective

 * Blade of Vaulted Secrets (quest)
 * Cape of Eternal Justice (quest)
 * Cloak of the Gathering Storm (quest)
 * Ring of Infinite Wisdom (quest)