This Datacron unlocks the codex entry - Galactic History 68: The Mandalorians Return
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:
The Mandalorians had never forgotten their humiliating defeat at the Republic's hands during the Great Sith War. With his Neo-Crusader warriors prepared by a decade of conquest, Mandalore the Ultimate decided the time was right and launched an assault on the Republic. Several Zabrak colonies fell to the Mandalorian advance, under heavy blaster fire and the shadow of Basilisk war droids.
Finally provoked into action, the Republic appealed to the Jedi for military support, but the Council refused. The Masters believed there were greater forces at work behind the Mandalorian invasion than a simple lust for war. They wanted to remain apart from the conflict, believing the true threat would reveal itself in time. However, some younger Jedi disagreed with the Council's edict. These Jedi would form a splinter group, the "Revanchists," and answer the Republic's call for help.
Coordinates X - 1913 Y - 476
NOTE: The Invisible Bridge to reach this Datacron was fixed in patch 1.2. The area we jump over in Screenshot 4 now is the only way to reach this Datacron. What you need to do is dismount off your speeder and jump down onto the bridge. From there you can reach the Datacron. Tread carefully!
This Datacron is located in the western section of The Tomb area of Belsavis. To reach this Datacron you must first jump ontop of a few rocks nearby located around -710 , -1943 (Screenshots 1 & 2). It's a very difficult jump to make, luckily it is the most difficult jump and it is the very first one. What you need to do is jump up onto the rock right in front of you in (Screenshot 1), you will want to keep trying this jump until you are where I am in (Screenshot 3).
From here run around the southern end of the lava pool following the rocks. The next jump is on the eastern most end of the lava pool, you have to jump over the vantage point of this Datacron (Screenshot 4). After you make this jump follow the southern rock ledge around until you reach a raised rock which seems like you wouldn't be able to jump onto (Screenshot 5). Getting onto this ledge is a bit tricky and I fell once trying to get up there so be careful! What you need to do is jump onto the side of the ledge, where I am looking in (Screenshot 6). And where I am standing in (Screenshot 7).
From here you will see a little lip of a rock coming out of this ledge which you can jump up onto to make it up onto the top of this rock ledge. Once you make it atop the rock ledge it's smooth sailing from there. You will want to head over to where I am in (Screenshot 8) and then from there you can jump down to where the Datacron is. You will want to try to land where I am in (Screenshot 9).