Once you accept the quest that Anduin is offering, two more pop up as well.

While he is fevered and incapable, Ren lets you know that the spirits down the hill are trapped and pained by their existence in Azeroth, unable to move on.  He requests that you put them to rest, if not for their sake, for his, as the cries of the dead are driving him mad.  To alleviate his suffering and theirs, you must kill six of the Tortured Spirits.

Lina has a request for the sake of her father as well.  According to her, her father has spent his life studying the ‘Vale of Eternal Blossoms’, a mythical valley sealed thousands of years ago, whose knowledge has been lost.  The presence of the pandaren is apparently because of a trail of clues leading to the cave down the hill, where a poem known as the Song of the Vale can be found- but it is guarded by an ancestor spirit, and Ren is in no condition to retrieve the thing.  She asks, therefore, that you defeat the spirit while you are in the cave, and return with the Song.  In addition to the usual rewards, she offers a new set of bracers to you.

Anduin, sadly, is of no help in combat.  Of much more interest is that he purifies the spirits after you have re-slain them, revealing that the people who lived here were jinyu.

The four waters are slightly more complicated- the first can be found just inside of the cave’s mouth, the Waters of Restorative Body.  There is a curving path up to the right of the pool, which leads you to another pool at the bottom of some ramps.  Up the ramps you can find the next waters, the Waters of Restorative Mind.  Two more paths lead upwards from there.  Heading to the right leads you to the platform where the pool where the Waters of Restorative Spirit wait to be collected.  Another ramp leads up from here, to a platform where the Shade of Ling Heartfist can be found, guarding the Waters of Restorative Heart, in addition to the scroll that holds the Song of the Vale.

Along the way, the spirits Anduin has purified have been hinting about being held by an evil that comes ‘from the ground’, so it is to be hoped that this greatest spirit will hold some answers.

The Shade of Ling Heartfist looks impressive thanks to its size, but it does little more than the other shades- striking at you and channeling or casting spells that deal Shadow damage.  It has a respectable amount of health, though, so expect it to take a bit longer than the other fights in the area.  Once the spirit is laid out, Anduin suggests that it may know something about the Song, and cleanses it.