Update 5.4's Timeless Isle will host the contest between little critters, creatures and creations.
One of the more interesting additions to World of Warcraft with the Mists of Pandaria expansion was the introduction of the Pokemon-esque Pet Battle system. Build up a stable of pets and use them to fight other pets for dominance and a strong ego boost.
With the release of Update 5.4 and the unveiling of the new Timeless Isle, the devs at Blizzard are launching a new Celestial Tournament where players will start a quest line that will have them taking on the pets of some of the more prominent members of Pandaren society, such as Chen Stormstout and Shademaster Kiryn.
Here are the basics:
Enter the world of Azeroth and battle against the Alliance of humans, dwarves and night elves or the brutish orcs, trolls and undead of the Horde. World of Warcraft has a very large community of players with hundreds of servers and a myriad of endgame pursuits from raiding dungeons, questing, achievement hunting, PVP arenas, and now pet battles.
Upon completing the quests and your first run through the Celestial Tournament, you'll be rewarded with enough Celestial Coins to purchase your very own Celestial battle pet. Each additional weekly attempt will continue to reward one Celestial Coin, which can be saved up and used to purchase the other three pets that will be available through a nearby vendor (progress will be tracked at the account level). Caring for these pets is a sacred honor, so each is account-bound and cannot be traded to other players.
To ensure only the best come out victorious, healing and reviving pets during the Scenario is strictly forbidden-so it's important to come prepared. To win, participants will need to defeat three random tamer teams, along with all four offspring of the August Celestials. Losing a battle from time to time will be inevitable, but that's not the end of the line. Though your defeated pets will remain down, you'll be able to restart the fight and adjust who's on your team before giving it another try. You'll also be able to switch up your team between battles. Should you happen to leave the Scenario before it's completed, you'll be able to return later to restart the event.
So start getting your pet training skills honed. You'll need level 25 pets to fill out your roster, and I seriously doubt your level 25 rabbit, squirrel or fawn will cut it.
Source: Official site