• Rune-Etched Nightblade
• Item Level 219Disenchants into:
  [Abyss Crystal]: 1-2
• Binds when picked up
  
• Sword
• One-Hand
  
• Speed 1.40
• 160 - 297 Damage
• (163.2 damage per second)
• +46 Agility
  +50 Stamina
• Durability 105 / 105
• Requires Level 80
• Equip: Improves critical strike rating by 32.
  Equip: Increases attack power by 56.
  Equip: Increases your armor penetration rating by 26.
• 
• Sell Price: 20 59 19

Source

This item drops from Assembly of Iron in the 10-man version of Ulduar.

Patch changes

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

External links

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