Patch 5.2 - The Thunder King will include a massive new raid dungeon, a multi-faceted new quest hub, Pet Battle improvements, new world bosses, significant class balance changes, brand new pets and mounts, assorted bug fixes, and more.
Throne of Thunder - new raid.
Emperor Lei Shen, the Thunder King, has returned to wreak his vengeance on Pandaria. It falls to the heroes of the Alliance and the Horde to stop the newly resurrected tyrant and his Zandalari allies in the massive new raid Throne of Thunder.
Throne of Thunder is a sprawling citadel housing 12 new raid encounters, and players that defeat Emperor Lei Shen in Heroic mode can earn the opportunity to face an additional 13th foe.
Join the Shado-Pan Assault in their singular drive to see Lei Shen, The Thunder King defeated once and for all, and gain access to impressive Valor reward items. Reputation with this faction can be earned only within the Throne of Thunder raid dungeon.
Nalak, the Storm Lord and Oondasta - new world bosses.
Nalak, the Storm Lord - after the Isle of the Thunder King has been conquered, the gate guardian of the Thunder King's citadel will appear. Players will frequently have the opportunity to test their mettle against him.
Oondasta - found in a place that has been lost in time, the great devilsaur lord Oondasta has been outfitted for battle with weaponry and armor by the Zandalari, and awaits players brave enough to seek him out on the mysterious Isle of Giants found in the seas north of Kun-Lai Summit.

The Darkmoon Faire has started and Patch 5.1 added a few new things. The biggest addition is the new Darkmoon Carousel, which takes the place of one of the large under construction tents. It uses the nice new music that was added in Patch 5.1. Riding it gives you the WHEE! buff, which increases reputation and experience gains by 10%. Unlike some of the other event buffs, it does work with quests as well, so it will be useful for leveling reputation. This buff will last for an hour if you ride long enough, but does not persist through death, so be careful!
Several classic raid bosses have been adjusted to be more friendly to solo players:
Viscidus - Viscidus now remains frozen for 30 seconds (was 15), and it takes 30 hits to shatter Viscidus (was 50).
The Twin Emperors - The recast time for Heal Brother has been increased to 3 seconds (was 2).
C'thun - Players now have 5 minutes to escape C'thun's stomach and resume the battle before it resets.
Al'ar - Al'ar and Ember of Al'ar are no longer immune to fire damage.
Reliquary of Souls - Spirit Shock now has a 15 second recast time (was 0 seconds).
Patch 5.2 Transmogrification Changes - Removing main-hand/off-hand Transmogrification restrictions maybe by 5.2. Also allowing Transmogrification of weapons from 2H axe to 2H sword, etc.

Patch 5.1 - Landfall is now live on all servers.
New Features
Item Upgrades - Items level 458 and above have a tooltip suggesting item upgrade. Rare items have 1 time upgrade allowing for 1500 Justice Points to increase that level by 8. Epic items have 2 times upgrade allowing for 750 Valor Points to increase item level by 4 twice.
Two new factions - Operation: Shieldwall(A) and Dominance Offensive(H) - New daily quests in Krasarang Wilds with new reputation gear Item Level 496.
Wrathion Quest Lines - The story line now continues.
Brawler's Guild - This new feature will be exquisite at first, allowing only people that bought Blood-Soaked Invitation from the Black Market Auction House to participate.
Pet Battle Updates - Now you can see the rarity of the pet, just by their icon color. The Pet Battle window also has been improved by adding frame colors corresponding to the rarity. You can sort pets in various ways and search pets for a given zone.
Loss of Control Alerts - Interface menu now have these new options showing you when you loss control of your character with a nice animation over you.
New Scenarios - Assault on Zan'Vess(A, H), A Little Patience(A), Lion's Landing(A), Dagger in the Dark(H) and Domination Point(H).
Class Changes

Reminder! The latest Normal difficulty Mists of Pandaria Raid dungeon is now available: Terrace of Endless Spring. All Heart of Fear bosses are also now available in Raid Finder.
To access the new Raid Finder dungeons, you will need to meet a minimum item level requirement of 470.

To help raiders prepare their schedules for next week, we wanted to give everyone a brief heads-up that the Normal mode Heart of Fear will be debuting alone on Tuesday, and the Normal mode Terrace of Endless Spring will now open two weeks following the release of Normal Heart of Fear.
To help players focus on tackling these new encounters without feeling overwhelmed, we've decided to stagger the release of the two remaining raid zones. Heart of Fear should prove to be a challenging zone that will take the typical group some time to master, and players must defeat the Grand Empress Shek'zeer at the end of Heart of Fear before they may move on to Terrace of Endless Spring once that zone unlocks.
The unlock schedule for Looking For Raid modes for Heart of Fear and Terrace of Endless Spring is unaffected by this change. Heroic Heart of Fear will still be accessible to players who have cleared the zone on Normal difficulty.

Patch 5.1 brings us a few new factions. All are associated with the Horde/Alliance forces landing in Pandaria or the Brawler's Guild, except for Akama's Trust.
Brawler's Guild
Underground fighting rings have sprung up in Stormwind and Orgrimmar that will give brawlers a chance to earn bragging rights by testing their solo PvE mettle against some of the toughest creatures found in World of Warcraft.
Players will prove their skill, and increase their rank with the Brawler's Guild, as they win matches against some of the most difficult solo encounters in World of Warcraft.
As their Brawler's Guild rank increases, players will unlock additional rewards and activities within the Brawler's Guild.
Brawlers on a realm will gather together into the blood spattered ring to watch as their peers face down their own opponents. They can watch the battles in progress to learn from hardened Brawler's Guild veterans as they wait for their own turn to fight.
If this is your first night at Brawler's Guild, you have to fight.
Black Temple Scenario
Wrathion Quest Line