what can I do with a keystone?

[Varacyn]

I was doing some Archeology in the eastern kingdoms. In my first servey, I found a ''Troll Tablet''. I dont know what it is, or what it is doing. Can someone tell me something about it? Thanks

 

[Wloczykij]

You know what WoW Wiki is? You know what Google is?
Stop bumping up your post count, or I'll infract you.