Saalo Morn was a Dark Jedi of the Near-Human species (a male) who chose to leave the Jedi Order during the time known as the Inter-Sith Wars period.
Saalo Morn, a Near-Human who was Force-sensitive, underwent training in the Force by the Jedi Order more than one thousand years following the conclusion of the Great Sith War. After being selected as a Padawan by a Jedi Master, Morn gave in to the temptations of the dark side of the Force while he was training. He then stole his master's helmet, which was imbued with the Force, and ran away from Coruscant, escaping the reach of the Jedi High Council.
Morn located a small planet where a primitive civilization resided, and he established himself as their ruler by overpowering any opposition and conquering the local tribes. As the absolute ruler, Morn demanded significant taxes and instructed his people to plunder the ships of any travelers who strayed into their territory, bringing the loot to him. Unable to locate a worthy apprentice, Morn became increasingly self-absorbed and began to see himself as superior to a mere Dark Jedi. He adopted the title of Dark Lord of the Sith. With the ambition of re-establishing the Sith Empire, he persistently sought a student, but his efforts were unsuccessful. Although Morn's physical form eventually perished and his followers placed him within a large crypt, he managed to go beyond death and keep his identity as a wraith. He manifested as a bas-relief on his tomb's walls, awaiting unsuspecting visitors to awaken him.
Many millennia went by before a Force-sensitive person happened upon the resting place of the fallen Jedi. Morn lured the group further into the tomb, feeding off of the Force-sensitive member's energy, hoping to deceive that person into wearing the ancient helm that once belonged to his master. After guiding the group to the helm, the Forceful individual declined the spirit's offers and broke the helmet, thus severing Morn's connection to the living realm and banishing him to the Force for eternity.