|Radagast the Brown|
'The sheer number of wights in Haragmar indicates the presence of gaunt-men, vile necromancers who serve the Dark Lord. In ages past, they dwelt in the Witch-realm of Angmar, but the White Council believed them all destroyed. Clearly, they were wrong.
'Only the strongest of the gaunt-men, the Gaunt-lords, have the power to summon the spirits of the Shadow Realm. The war-singers carry the sigil of their Gaunt-lord. Search the ruins in the far east of Haragmar, defeat these creatures, and bring me their sigils.
'We must learn which Gaunt-lord these creatures serve.'
Radagast is concerned with the cause of the corruption in the swamps. He feel that the wights are a symptom of a greater evil.
Radagast told you of the gaunt-men, necromancers in the service of Sauron, who are responsible for the emergence of these wights. He asked you to defeat the war-singers and bring him their sigils. He can then determine which of the Gaunt-lords they serve.
You would think the Gaunt Protectors would count, too, but no... they just hold the place where a War-singer might spawn. So you have to kill the Protectors while you move through looking for War-singers so the next circuit you might find some more War-singers.