If the vision that I granted you is true, then you must travel down into the ravine and to the south end of Bloodmaul Ravine. There you will find the Draenethyst Mine.
Journey to the back of the mine, and retrieve the Thunderspike. Ignore everything else! I have no interest in the crystals of the mine, nor the ogres therein.
As soon as you have the spear return it to me here!
And, <name>, be very careful with it... I would hate to think what would happen to you should you break it.
The significance of these artifacts eludes you, I am sure.
When we have all five, our right to the ownership of Thunderlord Stronghold will be secured through the appeasement of its dead spirits.
Do you begin to grasp now why this is so important? Do you understand why I have little patience for niceties?
Completion
Now I am impressed! Do you have any idea how many others died attempting to retrieve all of these relics?
We are fortunate to have you working with us here, <name>. Even if you are a bit slow.
You must allow me to reward your dedication to our cause. Choose, but choose wisely. When you are done, I will hand over the artifacts to appease the ghosts of Thunderlord Stronghold.
Notes
Garm Wolfbrother and friends
When you get to the back of the mine, you'll see the a spear (Thunderspike) on the ground. When you try to pick it up, an ogre named Gor Grimgut spawns. You have to defeat him to get the Thunderspike. It should be a relatively easy fight for anyone who made it this far into the cave.
When you complete the quest, you can now see several Thunderlord orc ghosts next to Rokgah. They lead to the next part of the chain.
Orcish ghost dialog
Three Thunderlord orc ghosts, and a ghostly wolf appear
Garm Wolfbrother whispers: <name>, you above all have earned the right for the Horde to inhabit our ancestral home.
Garm Wolfbrother whispers: By recovering the artifacts of our clan, by taking up the fight against our ancient enemy, the Bladespire ogres, and their gronn masters, by returning the Thunderspike to my hand, you have secured the blessing of the Thunderlord clan.
Garm Wolfbrother whispers: I have been watching you and Rexxar. You must aid him to secure the future of the Horde here in these mountains. Only when you have forced the ogres into submission and slain their master, Gruul the Dragonkiller, will your people be safe.