This quest is not available in game.
Slay Lord Azrethoc and Jugkar Grim'rod and return to Takata Steelblade in Desolace.
Although I have no knowledge of this Lord Azrethoc, I agree with Maurin, he must be stopped; especially if he is attempting to gain influence over the Burning Blade to further his goals.
You have already shown you wish to aid the Warchief, and I would trust you to gather a party to slay the demon lord and his warlock servant.
When you are ready, head directly south, and return to me when the threat has been ended.