• Sif's Promise
• Item Level 226Disenchants into:
  [Abyss Crystal]: 1-2
• Binds when picked up
• Unique-Equipped
• Finger
• +72 Strength
  +72 Stamina
• Requires Level 80
• Equip: Improves critical strike rating by 42.
  Equip: Increases your expertise rating by 42.
• "As shall my love never fail, neither shall the strength of your rule."
• Sell Price: 7 56 23

Source

This item can be found inside Cache of Storms after defeating Thorim in the 25-man version of Ulduar.

Patch changes

• Patch 3.1.0 (14-Apr-2009): Added. 
  

External links

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