Talk to Catelyn in Booty Bay.
The mage that is in possession of the Stone is amplifying its power through some focal point... an altar of some sort. You should be able to disrupt it by overpowering it.
As it happens, I know just the thing: an ancient dagger, another troll relic. There's just one... little problem.
You see, I found the dagger while researching in Stranglethorn, but I gave it to my willful daughter, Catelyn, who ran off to Booty Bay to become a pirate.
Hm, I haven't the eye to examine these bracers to see if any of them will be of any use, but I'm sure at least one of them will be able to help. Take them to Dalaran and have a <class> look at them.
After all, I can't very well leave Booty Bay just to chat with those tiresome old mages.
Not that I'm worried anyone would try to elbow their way into being the new baron. No one crosses Revilgaz and lives to tell of it.
Upon completion of this quest you will gain: