You can buy these only with the character that has reached rank 8 in Brawler's Guild.
at the Brawler's Guild to brawlers who have reached rank 8 with the guild: Quackenbush <Bizmo's Brawlpub Quartermaster>
The Brawler's Guild generally ends on the prepatch for the next expansion and does not start again for a few months after the new expansion launches. For Battle for Azeroth, the Brawler's guild started with patch 8.1. 5 and ended with patch 9.0.
The First Rule of Brawler's Guild
Once you have your invitation in place you can queue up to start a brawl by talking to Brawl'gar Arena Grunt or Bizmo's Brawlpub Bouncer. They will also tell you your place in the queue or you can check your Queued for Brawl buff.
Bizmo's Brawlpub is the Alliance Brawler's Guild. Found under the Stormwind City's station of the Deeprun Tram, Bizmo runs the action.
To get to Brawl'gar Arena
Getting to Brawl'gar arena is as easy as going to the Horde Capitol of Orgrimmar, heading to the Valley of Honor, and entering the large arena near the road heading north to Azshara. Get ready for action.
"Entry into the brawler's guild is by invitation only. Invitations can be found on the Black Market Auction House, by invitation from somebody within the guild, and occasionally as drops from certain Horde and Alliance NPCs."
To start this questline, you need to be level 120 and a member of the Brawler's Guild, so you can fight at the Brawl'gar Arena in Orgrimmar. If you became a member in previous expansions, you can sign up for fights even if you're not level 120, but you won't last long.
You can't get Bruce anymore.
Edit: Even if you have the achievement Now You're Just Showing Off (Season 1) and you reach rank 8 on other char, you won't get the title. You still need to kill 1 rare for the Brawler title.
The Brawler's Guild achievements were moved to Legacy, so it looks like the entire thing is going away. It's a shame when these things that added flavour and atmosphere are shut down.
Paul North is located inside the Brawl'gar Arena, which is in the Northern-most building in The Valley of Honor in Orgrimmar.
The mount Bruce is going to be unobtainable as BfA ends so get it now if you want it. : r/wow.
5 with a Murder Mystery Questline and plenty of rewards, including tabards, transmog sets and Bruce! To get into the Brawler's Guild you will need to be level 120 and have either a Blood-Soaked Invitation or Brawler's Pass which you can get by defeating enemies of the opposite faction in Zandalar and Kul Tiras.
Avarded to victors of the Brawler's Guild. Use it to purchase Rumble Cards and other world-altering items at the Brawler's Gold Exchange vendor.
History of the Brawler's Guild
Brawler's Guild returned in Warlords of Draenor, once again with eight ranks and Challenge Cards to summon specific bosses.
Shady is a human located in Deeprun Tram or the Valley of Honor of Orgrimmar.
Players at level 120 who have War Mode enabled will be able to queue for a Dueler's Guild battle at the Bouncers (Alliance) or Troll Guards (Horde) in the War Headquarters for their faction, located in Boralus and Zuldazar respectively.
There is one Brawler's Guild location per faction and per realm. The Alliance arena is located within the Deeprun Tram in Stormwind City (see at 01:23 in the above video). The Horde arena is located in the north-eastern building of the Valley of Honor in Orgrimmar (see at 00:39 in the above video).
Players at level 120 who have War Mode enabled will be able to queue for a Dueler's Guild battle at the Bouncers (Alliance) or Troll Guards (Horde) in the War Headquarters for their faction. Once you've queued, a buff will be placed on you showing your place in the queue.
This item can be purchased in Deeprun Tram (77) and Orgrimmar (23).