Study the tablets which tell of Ameth'Aran and of its fall, then return to Sentinel Tysha Moonblade in Darkshore.
To the east you will find the ruins of Ameth'Aran. It is now inhabited by the restless spirits of the Highborne that once dwelt within its walls, but once it was a place where the servants of Azshara freely practiced their powerful magics.
I was sent to explore the ruins and came across two large tablets, scrawled with the stories of Ameth'Aran and its fall. While I read the runes, I was accosted by the spirits, and fled.
Please, if you can, venture to the ruins and decipher the tablets in my place.