My former clan, the Felmusk of Night Run, raided Fallen Sky Lake some time ago, stealing the moonstones that were unique to the area.
Those moonstones are known to have great healing properties and surely can be used to cure the little girl that lies sick in Astranaar.
Night Run rests up the road to the east that runs north. There are multiple paths that lead up into the hills on its eastern side, and it is there that you will find my unrepentant brethren. They will have what you seek.