History
Naga Sadow fled to Yavin 4 following his defeat to the Galactic Republic in the Great Hyperspace War. He brought with him an army of Massassi warriors. He conducted experiments on these warriors using Sith alchemy, warping them from a Sith sub-species into dark Force-wielding monsters. Despite these heinous experiments, the Massassi still revered Naga Sadow as though he were a god. They constructed huge temples and filled them with many treasures as an offering to their master.
Upon completion of his temple, Naga Sadow encased himself within a Sith sarcophagus. He remained within this sarcophagus in a coma-like trance for centuries. His rest continued until 4,400 BBY, when Freedon Nadd, the fallen Jedi, arrived on Yavin 4. By this time, the remnants of the Massassi further devolved into a primitive hunter-warrior society. Not surprisingly, Freedon Nadd was attacked by the twisted monsters. However, his display of the Force persuaded the Massassi to show Nadd where Naga Sadow was resting. Nadd awoke Sadow from his centuries long slumber. Sadow then taught him in the ways of the dark side of the Force. In true Sith fashion, having learned what he needed, Freedon Nadd defeated Sadow and became the next Dark Lord.
Yavin 4 would remain relatively undisturbed until in 3,997 BBY when another fallen Jedi, named Exar Kun, arrived seeking the advice of the dark spirit of Freedon Nadd. The Massassi, however, attempted to sacrifice him to a dark side beast of alchemical origins beneath their main temple. Using his dark side power, Exar Kun saved himself and destroyed the spirit of Freedon Nadd, despite his attempts to ally himself with Kun.
Now the new Dark Lord, Exar Kun enslaved the Massassi and took over Yavin 4. Using Massassi slave labor, he constructed new Sith temples and palaces, based on Sith architecture. These buildings were designed to focus his dark powers. The Massassi soon rediscovered the flagship of Naga Sadow, and Exar Kun began new experiments into the dark side and created many vicious Sithspawn. Even more ghastly, the Sith Lord also imprisoned the souls of the children of the Massassi in a Dark Side device known as the Golden Globe.
With the construction of the temples complete and Exar Kun's powers growing, he allied himself with a group of dark side users known as the Krath. These dark Force wielders were under the leadership of Aleema Keto and a fallen Jedi known as Ulic Qel-Droma. Realizing that further power was within his grasp, Kun sought the Jedi world of Ossus. He recruited twenty Jedi to his cause, forming the Brotherhood of the Sith. In 3,996 BBY, Exar Kun along with his Krath and Mandalorian allies waged war on the Republic and the Jedi. The Jedi eventually managed to push Exar Kun and his allies back and gathered their forces for an assault on Yavin 4. As the orbiting Jedi fleet attempted to obliterate the dark side users, Kun gathered his Massassi followers into the Great Temple and drained their life energies. In doing this, he freed his spirit from his body and invested it into the surrounding structures where he would remain for millennia.
In 3,756 BBY, Jedi Master Barel Ovair and his Padawan Eison Gynt traveled to Yavin IV to explore Naga Sadow's tomb. The Jedi found that Sadow's Massassi warriors survived the bombardment of the moon during the Great Sith War, and were promptly attacked by the beasts. They fled deep inside the temple that once housed Naga Sadow's body. After all was said and done, only Ovair returned to Coruscant. The Jedi Master lied to the Jedi Council and claimed that Gynt was killed. However, Gynt was still alive, and eventually returned to Coruscant possessed by Sadow's spirit. Gynt fought Ovair, but was slain. Later, Jedi historian Gnost-Dural revealed that Ovair was in reality a Sith infiltrator from a family of infiltrators. His orders from the Sith Emperor were to seal Naga Sadow's spirit, so that the dead Dark Lord would not interfere with the Emperor's plans.
Speculation
Yavin 4 possesses many dark side temples that may still contain treasures. These treasures could include dark side artifacts and tomes which would certainly add to the power of those that seek them out. It wouldn't be a stretch to guess that raids or flashpoints would be included on Yavin 4. Exar Kun and Naga Sadow experimented with Sith alchemy and created all sorts of Sithspawn that could be fought and defeated. In addition, the Massassi that still exist on the planet are mindless beasts only interested in the destruction of outsiders who land on the planet. These "dark force wielding monsters" would make Yavin 4 an extremely rough place to visit.
Yavin 4 was corrupted by the dark side since Naga Sadow first came to planet almost 1500 years ago. Such corruption could affect the native plant life, creatures, and even the environment itself. Time and time again, fallen Jedi came to Yavin 4 in an attempt to seek a Dark Lord that could instruct them in the dark side of the Force. This idea could imply that Dark Jedi on the Galactic Republic side are capable of going here in an attempt to hone their dark side skills or seek artifacts to amplify their power. The same could be said for Sith that desire to strengthen their powers.
The Massassi are a major factor every time a new visitor arrives on Yavin 4, as they either seek to destroy newcomers, or honor them with gifts and submission. It is possible that capable players may be able to gain the loyalty of the Massassi, gaining a companion character in the process. This would make more sense if the character was a dark side player, but perhaps players of any alignment would be capable of corrupting or purifying their Massassi companion.
Yavin 4 is an iconic planet that symbolized corruption and the dark side throughout most of its history. This remained true until after the Battle of Yavin, when it was thought of as a symbol of a new hope. This shows that no matter how dark or how light, there is always the potential for things to be turned upside down. Yavin 4 would be a welcome addition to the growing list of playable planets.
Sourceshttp://starwars.wikia.com/wiki/Yavin_4http://www.swtor.com/info/holonet/timeline/peace-republic
