• Sigil of the Vengeful Heart
• Item Level 226Disenchants into:
  [Abyss Crystal]: 1-2
• Binds when picked up
  
• Sigil
• Relic
• Requires Level 80
• Equip: Increases the damage done by your Death Coil and Frost Strike abilities by 380.
• Sell Price: 6 92 79

Source

This item drops from XT-002 Deconstructor 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