Darkmoon Dominator

>>>~~~ This is from the new Darkmoon Deathmatch Event ~~~<<<

To get this achievement you must loot 12x [item=74034] and complete the quest they give you. Doing so will also award [item=74035].

To get [item=74034], you must be at the Darkmoon Deathmatch Arena when the special chest spawns. It spawns every three or so hours at approximately the following server times:

00:00 (Midnight)
03:00
06:00
09:00
12:00
15:00 (3:00pm)
18:00 (6:00pm)
21:00 (9:00pm)

In addition to being at the chest, you must defend yourself if some else is seeking the treasure. Even if they are from the same faction!

Accoridng to Blizz: (Source)

Like any good carnival, the Darkmoon Faire has a shady side. You can leave the skilled labor to the suckers and go for a faster score instead. If you’ve got the minerals, the Darkmoon Deathmatch offers an experience unparalleled since the Gurubashi Arena. Pitmaster Pei has a big old treasure chest just brimming with goodies and Darkmoon Faire Prize Tickets that he’ll drag out into the Darkmoon Deathmatch Pit every three hours or so. Everybody wants it, so if you want a piece of the action you’ll just have to jump in and prove that you’re the toughest one in the Pit.

Silly stuff, "... jump in and prove that you’re the toughest one in the Pit."

Or most usually just the one with more fellas cowering your back while you fill the cast bar to open the box. Meh...

You don't need to have more skill, better gear, or anything like, just get more friends to CC and kill everyone else that enter arena and have an easy win.

I can confirm that the Pit Fighter trinkets do not stack.
You'll need 12 inventory slots for this.