Tablets of Baa'ri is the start of a long quest chain which involves the Broken clan known as the Ashtongue Deathsworn. This quest starts with a different person depending if you are allied with the Aldor or the Scryers. This quest starts the beginning of the Black Temple attunement.
The Ruins of Baa'ri are at coordinates 55,35 in Shadowmoon Valley. The tablets can be found on the ground as well as drop off the Ashtongue Workers.
Description
Aldor Version
Years ago, the dreaded warlock known as Gul'dan raised the volcano in the middle of Shadowmoon. The draenei village of Baa'ri, to the southwest, was buried under the lava along with its inhabitants and artifacts of religious importance.
The treacherous tribe of Broken known as the Ashtongue has been ordered by Illidan to excavate the area. We must use this opportunity to recover the Tablets of Baa'ri, an ancient text rumored to hold the secrets of the Temple of Karabor, now known as the Black Temple.
Scryer Version
The Ashtongue Broken have been ordered by Illidan to excavate the Ruins of Baa'ri, to the far north. They're in search of draenei artifacts, no doubt - Baa'ri was home to many Baa'ri relics before Gul'dan buried the town under a volcanic explosion. We must use this opportunity to recover the Tablets of Baa'ri, an ancient text rumored to hold the secrets of the Temple of Karabor... a place you might know as the Black Temple.