The Human male who would one day be known as Darth Nihilus, Dark Lord of the Sith, was alive at the conclusion of the Mandalorian Wars, a galaxy-wide conflict between the Mandalorian Neo-Crusaders and the Galactic Republic. Amidst those battles, he lost everything: his family, friends, as well as his will to live. He was on the planet of Malachor V during the final battle of the war in 3960 BBY, when Jedi General Meetra Surik gave the order to activate the Republic's Mass Shadow Generator superweapon. The generator killed almost everyone on the planet's surface and in orbit nearby.  

The future Dark Lord survived the superweapon's destruction of the surface and assumed a dark persona while grieving his losses, in part as a means of survival. He was trapped on the planet by the artificially-created mass shadows along with the bulk of the opposing, disabled fleets that filled space around the planet—where the Mandalorians had committed all of their forces in a last attempt at defeating the Republic—and took ill suddenly due to the shadows' effects. His emotional pain then manifested as an emptiness that swept over his idle body and it soon began to manifest as an intense "hunger." Without intent, he drained the life-force of another survivor. The act was an unpleasant experience for him, but the hunger and his painful memories faded for a brief moment alongside his sickness. Nonetheless, the emptiness returned more relentless and severe than before. He indulged in absorbing the energy of other survivors, but, the more he fed, the shorter the hunger was appeased and the more powerful it became.  

After the Dark Lord of the Sith Darth Malak was killed at the Jedi Civil War's conclusion in 3956 BBY,the Sith Empire became divided and its followers turned on each other, with many factions rising to stake claim to what little power could be garnered. The man was eventually discovered by the Dark Lord Darth Traya, who had sensed him as a wound in the Force. After locating him, Traya explained that it was the Force that fueled his hunger and offered to train him to devour entire worlds to help appease the hunger at her school on the planet, the Trayus Academy. He followed her there and learned the ways of the Sith alongside another prospective Sith. Traya's hungry pupil and her other apprentice each honed different aspects and skills of the dark side of the Force, until they both became Sith Lords. The man took up the name Darth Nihilus, while the second apprentice became known as Darth Sion, and they joined with Traya in the creation of a Sith Triumvirate. In addition, the three each took a unique title, with Nihilus selecting "Lord of Hunger."