Quest:The Mastermind

Objectives
Locate and kill Z'kral in the mines beneath Honor Hold, then report back to Foreman Biggums.

Z'kral slain

Description
Those infernal gan'arg keep scurrying into the mine! For each one you kill, two or three more seem to take its place!

There's got to be someone down there in the deepest reaches of the mine directing the incursion. You seemed to do well against them last time, and Light knows you're the only one brave enough to venture back into the mine. Find out who's responsible for this disturbance and make him pay!

Rewards
You will also receive:

Gains
Upon completion of this quest you will gain: 9800 xp or at level 70.

+250 Honor Hold faction

Completion
I'm glad you managed to take care of, of... what did you say he called himself? Z'kral?

From your description, it sounds more like an 'it' than a 'him' but all that matters is it's dead.