This Datacron unlocks the Codex Entry - Galactic History 55: The Ascension of Exar Kun
This datacron holds unheard of power and knowledge collected by an ancient race. You access its power and discover writings which are clearly only one small piece of a massive galactic history:
On the advice of the spirit of the Sith Lord Freedon Nadd, the fallen Jedi Exar Kun traveled to the jungle moon of Yavin Four and encountered the Massassi--the primitive servants of the dead Sith Naga Sadow. The Massassi took Exar Kun prisoner and prepared to sacrifice him to a monstrous wyrm.
Exar Kun was forced to use his growing connection to the dark side to free himself. Freedon Nadd appeared once more, congratulating his student. But Exar Kun had tired of Nadd's meddling and used his newfound strength to obliterate Nadd's spirit. Cowed, the Massassi bowed before Exar Kun as his slaves.
Exar Kun's power grew. He ordered the Massassi to build immense temples and to seek out Naga Sadow's lost battleship. He also used Sith alchemy to create horrific monsters, including terentateks that hungered for the blood of Force users. But powerful as he was, he could sense a distant rival: Ulic Qel-Droma.
Coordinates: X -778 , Y 107
To reach this Datacron you first will need to fly to Lower Markaran Outpost in Balmorra. From here you will be following the road south through the Markaran Plains and across the bridge to Gorinth Canyon. Once in Gorinth Canyon you will notice an extremely large AA gun as well as a pipe that runs across the gorge (Screenshots 1 & 2). From here you will want to... You guessed it, go across the pipe to the large mountain-like thing and make your way across the hidden path.
At the end of the hidden path you will see the Datacron down below sitting harmlessly on a ledge (Screenshot 3). From here it is a simple task of just jumping down to the Datacron. Be careful though, if you miss a jump you will need to fly back to Lower Markaran Outpost and start this little trip all over again.