Scourgebane Infusion

Scourgebane Infusion is a one-use potion that gives you a temporary buff to your spell damage against undead. As a quest reward from Tranquillien, it is only available to Horde players.

Source
This item is a reward from the Tranquillien quests Spinal Dust and More Spinal Dust which start with Magistrix Aminel in Tranquillien in Ghostlands. To complete these quests, you must turn the following items to Magistrix Aminel:
 * 10 Spinal Dust