Arcanum of Protection

The Arcanum of Protection is a enchanted gem that will add a dodge bonus effect to either a head or leg item. This effect will not stack with other enchantments on the item.

Source
The Arcanum of Protection is a quest reward from the quest Libram of Protection (quest) which starts with Lorekeeper Lydros in Dire Maul. To complete the quest, you must turn the following items:
 * 1x Libram of Protection
 * 1x Pristine Black Diamond
 * 2x Large Brilliant Shard
 * 1x Frayed Abomination Stitching

As a quest objective

 * The Savage Guard - Arcanum of Protection