• Arcanum of Shadow Warding
• Item Level 70Disenchants into:
  Not disenchantable
• Binds when picked up
• Requires Level 70
• Requires Lower City - Honored
• Use: Permanently adds 20 Shadow resistance to a head slot item. Does not stack with other enchantments for the selected equipment slot.
• 1 Charges
• Sell Price: 25

Source

Sold by  Nakodu <Lower City Quartermaster> in Shattrath City for 100 when you reach honored reputation with Lower City.

Patch changes

/ Patch 3.0.2 (14-Oct-2008): Renamed "Arcanum" (was "Glyph") to not confuse with Inscription glyphs. 

External links

• Battle.net (EU)
• Wowhead
• Thottbot
• WoWDB