For those interested in lore and whatnot for the Isle of Thunder and our reasons for taking it:
Scout Captain Elsia's conversation on the flight over..
Scout Captain Elsia says: Pandaren legends tell of Lei Shen, "The Thunder King." He was the brutal founder of the Mogu empire over 12,000 years ago.
Scout Captain Elsia says: He united the mogu, defeated the other pandaren races, and founded a glorious nation with the slave labor of those he conquered.
Scout Captain Elsia says: The Thunder King built a palatial fortress on the borders of his empire. We should see it soon...
Scout Captain Elsia says: There! Just ahead: The Isle of the Thunder King.
Scout Captain Elsia says: The Pandaren are terrified that the former Emperor will try to reclaim his empire, and enslave them once again.
Scout Captain Elsia says: But we have our own reasons for assisting them. I will allow Lor'themar to explain.
Scout Captain Elsia says: Whoa! Careful - it is nearly impossible to fly anywhere near the island!
Once you have turned the quest in to Lor'themar, the speech is continued by Lor'themar.
Lor'themar Theron says: Aethas, leave us for a moment.
Lor'themar Theron says: Hero, you have served the Horde nobly across many campaigns. I feel I can take you into confidence.
Lor'themar Theron says: Our Warchief's campaign across Kalimdor and Pandaria is pulling the Horde apart at the seams.
Lor'themar Theron says: We are here to fight the Thunder King. Justice demands it, and Hellscream is too preoccupied at Domination Point to pay attention here.
Lor'themar Theron says: But, in defeating him, we must seek out the source of his great power. We must claim it for ourselves, as leverage against our "Warchief."
Lor'themar Theron says: In the event of an uprising, we must be prepared.
Lor'themar Theron says: Heads up!
Lor'themar Theron says: Ha-hah! It will feel good to bloody my blade again. Against Alliance or mogu, does not matter to me.
Lor'themar Theron says: Enough talk. You know how precarious our position is. Between the Alliance and the Thunder King, only with the help of heroes like you can we hope to succeed here.
Lor'themar Theron says: Anar'alah belore, hero. Good luck.