The mask of Darth Nihilus, or Mask of Nihilus, was one of the pieces of armor that Sith Lord Darth Nihilus had bound to himself using the Force in an effort to retain a semblance of a physical form. Darth Nihilus had been one of the few who had survived the activation of the Mass Shadow Generator while on the surface of Malachor V during the last battle of the Mandalorian Wars, the Battle of Malachor V. This experience left him with an insatiable need to feed on the Force. Eventually this hunger began to erode his physical body and in an effort to keep himself alive, he bound his spirit to his armor, robes, and mask using the dark side of the Force. At the end of the First Jedi Purge Nihilus was killed aboard his flagship, the Ravager, by Meetra Surik, his former apprentice, Visas Marr, and the current Mandalore, Canderous Ordo, leaving his mask as a gruesome reminder of his reign as the Lord of Hunger.
This mask was considered to be a Sith artifact that encouraged the wearers to slowly destroy themselves for greater power. The lost mask of Darth Nihilus was imbued with the dark energy of the Sith Lord, allowing any who wore the ghost-white mask the power to wield the Force as if they were a Sith apprentice.
Later, the mask was recovered from the crashed smuggling ship, Nashuaga, on the planet Volik.
Sometime between 3960 BBY and 3952 BBY the ravages of an insatiable dark hunger for the Force destroyed Darth Nihilus‘s physical body to the point where he was compelled to bind his life-force into his robes and armor—including a facial mask—in order to avoid death and give himself a palpable form which allowed him to wield a lightsaber and continue his mastery of the Force. Darth Nihilus’s mask continued to serve its purpose until his death at the hands of the Jedi Exile and her companions in 3951 BBY.
For the next four thousand years, rumors spread across the galaxy concerning the mask’s power. It was said that the mask was invested with the dark side of the Force and if an individual who was not Force-sensitive was to don the mask, that being would be able to wield the Force as a Sith apprentice. If, however, a Jedi or Sith was to wear the mask, proficiency in additional Force powers—always including, but not limited to, dark side powers—were acquired. However, it was cautioned that the dark influence of the mask propelled the wearer towards acts of self-destruction in the pursuit of greater power.