Speak with Runok Wildmane at the Argent Tournament Grounds to become a valiant of Thunder Bluff.
You've proven yourself worthy of competing under the banner of Thunder Bluff, <name>. Now, you should speak with Runok Wildmane, who leads Thunder Bluff's competitors. As Thunder Bluff's grand champion, he will enter you into the tournament on behalf of the city and oversee your training and testing as valiant.
It has been an honor working with you, <name>, and I wish you luck in the competition ahead.