The Cargûl, Mâb Rhûnadan, dwells among the ruins of Sâd Morangol, using a corrupt altar to summon fell spirits to Taur Morvith.
'I have found where the Enemy conducts the rituals to summon fell spirits to Taur Morvith. There is an altar in the crumbling cellar of one of the ruins to the south-east...but I also found out what power is behind it. There is a Cargûl -- one of the cursed knights of Eärnur -- hiding somewhere in those ruins! I have heard his name whispered by his servants. He is known as Mâb Rhûnadan.
'I consulted Agorin on the matter. It seems that this creature is a favoured apprentice to one of the Nine, and a powerful sorcerer in his own right. Be very careful should you encounter him!
'If you can make your way to the altar and destroy it, that should put an end to their power here for the time being -- barring that, you may have to destroy the Cargûl himself. I also doubt he will allow you to interfere with his place of power unmolested.'
Mâb Rhûnadan and his altar may be found at Sâd Morangol.
Ianudirel has asked you to destroy the altar of Mâb Rhûnadan or defeat the Cargûl himself.
Ianudirel is just south of the bridge at Krul Lugu.
You should return to Ianudirel with news of your success.