Rift Quest:Bound in Death  

This quest takes place in Expert Runic Descent. After you encounter Wormwood, you will encounter a few trash mobs followed by Rasmolov's Construct. Kill the construct and loot Rune of the Void Knight Scroll. Return to Rurik to complete.

CORRECTION: ACTUALLY the construct is after the 3rd boss 'Warden Falidor,' after him you will fight a few sets of trash mobs and then you will come across Rasmolov.