Dreadstone

Source
This item can be obtained via the following means:
 * Prospecting Titanium Ore
 * Alchemy level 450 - Transmute: Dreadstone (Twilight Opal + Eternal Shadow)
 * Icy Prism has a chance of yielding an epic gem.

Jewelcrafting

 * Accurate Dreadstone
 * Defender's Dreadstone
 * Etched Dreadstone
 * Glinting Dreadstone
 * Glowing Dreadstone
 * Guardian's Dreadstone
 * Infused Dreadstone
 * Mysterious Dreadstone
 * Puissant Dreadstone
 * Purified Dreadstone
 * Royal Dreadstone
 * Shifting Dreadstone
 * Sovereign Dreadstone
 * Tenuous Dreadstone
 * Veiled Dreadstone

Prior to patch 4.0.1 Dreadstone was also used for crafting the following:
 * Regal Eye of Zul