This quest is not available in game.
Venture forth into the Tainted Scar and locate a Doomguard Commander.
Use the Glowing Crystal Prison on the Doomguard Commander. Be prepared for a ferocious onslaught of attacks, as the demon attempts to escape capture.
Should you succeed, return the Imprisoned Doomguard to Daio in the Tainted Scar.
The prison is ready. Now for the most difficult portion of this task.
You must find and capture a Doomguard Commander within the Tainted Scar using this crystal prison.
Be warned! A Doomguard is a cunning and lethal adversary and will seek to destroy you as you begin the ritual of imprisonment. It will flail wildly in its attempts to escape imprisonment.
It will focus on nothing but you, <name>. Because of this, I must recommend that you take companions capable of keeping you alive!