My next task was to kill gaunt-men and collect 5 sigils. These are servants of the Gaunt Lords, necromancers who serve the Dark Lord. The sigils will tell Radagast which Gaunt Lord we are dealing with.
They summon weak pets so I found my traps very useful here. I collected the 5 sigils Radagast needs and returned to Ost Guruth.
The sigils bore the mark of Ivar the Blood-hand and Radagast believes that he is behind the corruption of the Red Swamp. Radagast could not fathom why he was drawn here though.