Beasts of various origins have been causing problems for the dwarves in the Misty Mountains, including Gróthurs, whose endless boulder hurling endangers all mountain explorers.
'Stone-giants have no respect for the mountains! They spend all day throwing boulders at each other while trees and animals are flattened and killed without their knowing!
'One particular giant, that we call Gróthurs, has made it impossible to venture through these mountains. Could you talk some sense into that imbecile?!'
Gróthurs can be found somewhere in The Misty Mountains.
You should defeat Gróthurs.
Authi can be found in Glóin's Camp in the Misty Mountains.
You should speak with Authi.