• Kingsbane
• Item Level 219Disenchants into:
  [Abyss Crystal]: 1-2
• Binds when picked up
  
• Dagger
• One-Hand
  
• Speed 1.40
• 182 - 274 Damage
• (162.9 damage per second)
• +46 Agility
  +34 Stamina
• Durability 75 / 75
• Requires Level 80
• Equip: Improves hit rating by 36.
  Equip: Increases attack power by 70.
  Equip: Increases your expertise rating by 23.
• "The blade carries with it a sense of deep sorrow."
• 
• Sell Price: 22 33 57

Source

This item drops from Yogg-Saron in the 10-man version of Ulduar.

Trivia

This is most likely the dagger that Garona Halforcen used to assassinate Llane Wrynn.

Patch changes

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

External links

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