This is the second round of the Frostmane Troll Saga initiated by The Troll Cave quest, which you must have completed first. You begin it by speaking to the already upset Grelin Whitebeard who will say:

My journal! They took it away to the cave. The one that had it... It was a big brute with some odd markings on his skin and face. I didn't get a much better look than that.

You've had some luck with the trolls, maybe you could go get it back for me?

Kill Grik'nir the Cold
Loot Grelin?s journal

Find your way into the troll cave south of Grelin?s camp. In here you will find Young Frostmane Trolls (level 3-4) and further inside you might see Frostmane Novices (level 3-4). There are several branches in here, but if you look for the largest of the caves with a small lake in the middle you will see Grik?nir the Cold (level 5) standing in there with a long sword. Some characters will be able to kill him alone, while others might need a group to help. When you?ve killed him and looted the journal, head back to Grelin who will say:

Wonderful! Many thanks for retrieving my notebook. Well, it would seem that the troll situation here in Coldridge is under control and not much cause for worry.

After I put the finishing touches on my report, I?ll need someone to courier it to my brother Senir.

Completing this one will begin Senir?s Observations I and send you out of Coldridge Valley.