Locate Jandice Barov in the Scholomance and destroy her. From her corpse recover Krastinov's Bag of Horrors. Return the bag to Eva Sarkhoff.
This NPC or object can be found in Western Plaguelands.
Here you can buy Krastinov's Bag of Horrors for EU or US Servers.
You'll get guide for getting Krastinov's Bag of Horrors
• Krastinov's Bag of Horrors
