Talk to Wodin the Troll-Servant at the Crucible of Carnage in Twilight Highlands.
You've got some fight in you, <class>. You might do well in the crucible.
What!? You haven't heard of the Crucible of Carnage? That smarmy goblin Gurgthock and his troll sidekick have been plastering us with leaflets ever since he set up shop here in the Highlands. Champions from all over Azeroth fight to the death in there. You should gather up some friends and see how you fare.
The Crucible is just to the southwest. Look for Wodin the Troll-Servant somewhere in the middle of a ring of bones.