Thane Béortnoth sent you to investigate a location where he saw smoke and ashes rising near the eaves of Fangorn, and you discovered a battlefield where the bodies of Orcs had been piled and burned. There was also a mysterious old man awaiting you.
'If you wish to truly give Thane Béortnoth and his people hope of surviving the Orc-invasion, you will need to cut off the Orcs from reinforcement.
'To the north-east of here, there is an encampment of goblins and Wargs called Thrug-unur. The goblins there came down from Moria in pursuit of that Company of which you know, but which I will not name, and were pressed into service by Saruman's Uruk-hai.
'Enter Thrug-unur and deal with the captain of the goblins, Zân...cut the head from the serpent, and the body will die. Return to me when the deed is done.'
Zân can be found at the goblin-camp of Thrug-unur, north-east of Éomer's Vengeance.
The mysterious old man suggested that you defeat Zân, the captain of the Moria-goblins, in hopes of cutting off the reinforcements from Thornhope.
The mysterious old man can be found at Éomer's Vengeance, south-west of Thrug-ulur.
You should return to the mysterious old man with news of your success.