Darth Azaroht

Darth Neyhos was a Sith Lord during the time of the. He was said by his followers to have been so cruel and so evil that even the other Sith Lords feared him. It took the combined efforts of the entire Jedi Order to defeat him. After he was destroyed, his soul was locked away for all eternity deep inside a temple of Korriban.

Origins
Records are inconsistent as to the true identity of Darth Neyhos. Most believed that he was once a Jedi Knight who turned to the dark side of the Force. He first came under the tutelage of Darth Garsios.

The Rise of Darth Neyhos
After Garsios had taught Neyhos everything he knew, Neyhos killed his master and eventually assumed control of the Sith Order. He waged a massive campaign against the Republic and nearly succeeded in conquering it. He nearly crushed the Jedi Order, with less than a hundred Knights still remaining. For the next thirty years he ruled his new empire with an iron fist. He also trained to become the complete master of the dark side. He was said by his followers to have grown so powerful that even the other Sith Lords began to fear him. Several tried to assassinate him and assume control of the empire, but none prevailed. Eventually, he learned how to use the dark side to bend reality to his will and began altering the galaxy into a twisted version of itself.

Downfall
Meanwhile, The last remaining Jedi Knights formed an underground resistance to Neyhos' rule. They were lead by a Jedi Knight known as Galen Nestina. He managed to convince many other races to join his side. But there was a traitor among them. A spy revealed the insurrectionists location to Neyhos. Neyhos was furious but not worried. He believed that he was invincibe and no force could possibly challenge him. He sent his massive army to crush the rebellion.

The ensuing battle lasted for weeks. After his army nearly defeated Galen's forces, Neyhos himself arrived on the planet so he could personally crush any hope of rebellion. He demanded that the leader of the rebels face him one on one. Galen stepped forward to face Neyhos. The two began a furious duel. Legend says that the battle was so fierce that the ground shook. The two battled for three days without a clear victor. On the dawn of the fourth day, Galen finaly gained the upper hand and impaled Neyhos with his lightsaber. In a wave of dark energy, Neyhos' body exploded. The blast was so powerful that all of Neyhos' followers were killed. But shortly after his victory against his nemesis, Galen died from exhaustian.

Aftermath
Neyhos' spirit was sealed behind an impenitrable door on Korriban. There was only one way that he could escape. A group of Jedi Knights forged a key and pledged to stay on Korriban and prevent Neyhos from ever returning. This brotherhood was known as the "Legion of Light". For thousands of years they guarded the door. Over the years, the history of Darth Neyhos became scarce until eventually he was forgotten completly. Only the Legion of Light remembered his reign of terror.