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Warning: Spoilers for patch 5.2 content incoming! Don't hit the link if you don't want to know what happens or why the Alliance and Horde are here!
On the Alliance side, you'll then be directed to Vereesa Windrunner of the Kirin Tor at the Shado-Pan Garrison in Townlong Steppes. After flying, she'll immediately place you on a mount and escort you to see Jaina who just so happens to be waiting for you on the Isle of the Thunder King. Along the way, Vereesa will explain to you the history of the Mogu Empire. Eventually, you'll settle upon a small fleet of Alliance ships just south of the island under fire from land-based siege weapons. Thankfully, the Kirin Tor have augmented the fleet with powerful shields capable of repelling these missiles. When you find Jaina, she'll instruct you to secure the island for the Kirin Tor and ensuring Lei Shen's power does not fall into the hands of the Horde.
For the Horde side, you'll be sent to see Scout Captain Elsia for the Sunreavers (also near the Shado-Pan Garrison). We're wanted by the Lord Regent Lor'themar himself. The captain will also offer a little background history on the Isle of the Thunder King and Lei Shen. Once you arrive in front of Lor'themar, he'll take you aside and mention how Garrosh's campaign is gradually splitting the Horde apart. While they're supposed to be here to engage the Thunder King, Garrosh is too busy to care as he is overseeing Domination Point. Their goal is to secure Lei Shen's power and claim it as "leverage" against the Warchief in the event things don't work out so well between them and the rest of the Horde.
Two factions with the same goals but for different reasons. Who will you support in this escalating conflict?