Ichor of Undeath

Source
This item drops from level 37-61 undead mobs found in Kalimdor and Eastern Kingdoms.

Alchemy

 * Elixir of Greater Water Breathing

Blacksmithing

 * Blight (polearm)

Engineering

 * Gnomish Death Ray

Tailoring

 * Soul Pouch

Enchanting

 * Enchant Cloak - Greater Resistance

As a quest objective
The Ichor of Undeath