For over a millennium, the wicked phantom of a long-gone Sith Master (in Legends continuity) acted as the guardian of a forgotten spellbook. This book was concealed within a secret armory brimming with dark side knowledge, deep within the jungles of the planet Onderon. A few years prior to the Great Sith War, Shas Dovos, a young blacksmith, stumbled upon the book that the spirit protector watched over. The Sith apparition corrupted Dovos and trained its unwitting apprentice for more than a decade. Eventually, under the Master's hidden direction, the blacksmith forged a suit of armor infused with Sith magic. The spirit then revealed its true identity and its grand scheme: to resurrect the lost glory of the Sith Empire. It rechristened the apprentice Warb Null and, using the power of the dark side of the Force, descended upon him with the magical armor, binding man and metal together.
A deceased Sith Master's spirit was both contained within and served as the guardian of a book of sorcery. For well over a thousand years, this entity protected the volume from the ravages of time and other dangers. Unable to personally bring about the resurgence of the legendary Sith Empire of old, the spectral guardian hoped to find someone worthy of its power. More than a decade before the Great Sith War, the spirit protector allowed a young blacksmithing student named Shas Dovos to discover its literary prison. Dovos found the tome in an ancient dark side bunker buried deep within the jungles of the Inner Rim world of Onderon. Dovos absconded with the book, and the spirit protector recognized the potential to turn him into an unknowing pawn.
For over ten years, the spirit protector concealed its clandestine manipulation as it taught Dovos—slowly and subconsciously—the intricacies of Sith magic. Small bits of knowledge were imparted, causing Dovos to abandon all other pursuits in his quest for the ancient spirit's wisdom. The protector often planted suggestions in the apprentice's dreams, hinting at a glorious destiny achievable through his craft and amplified by ancient Sith rituals. Many attempts to create an object of power failed until, on the fourth night of one such endeavor, the spirit protector's apprentice finished his masterpiece: a blackened suit of armor imbued with the dark side of the Force.
Dovos was initially hesitant to use his creation, but the spirit protector's subtle prodding, through mental coercion, restored his confidence in his craftsmanship. Confused by the mental intrusion, Dovos cried out as the spirit protector, appearing as cinders, confessed its involvement in his life since he discovered the spellbook in the jungles of his homeworld. With a burst of energy, the spirit protector shifted from its alien–like form into a fiercely expressive near-Human appearance. It then approached its terrified thrall, commending him for following its commands. The spirit protector revealed that it had orchestrated the ability to understand the spellbook and create the armor, tasks the young blacksmith would have been incapable of otherwise. However, the spirit demanded payment for its gifts. Dovos was to become an extension of its will, furthering its agenda whenever and wherever it could not.
The apprentice expected oblivion, but the spirit protector assured him that destiny had reserved a special place for him: Dovos would participate in the restoration of the long-forgotten Sith Empire. Before he could begin his new task, the spirit protector needed to empower Dovos, choosing the armor as the means to do so. To symbolize his rebirth, Shas Dovos was renamed "Warb Null" by the spirit protector, a name it deemed fitting for a being whose new existence would be a fusion of flesh and metal. It then engulfed Null and, using Sith magic, bound him to his armor—the pinnacle of his former existence. Null became a Dark Jedi and was chosen to guard another Force entity, the spirit of the long-dead Dark Lord of the Sith Freedon Nadd, in whose name he participated in an attempted revival of Sith prominence, just as predicted by the spirit protector.
Thousands of years later, the failed Jedi Padawan Telloti Cillmam'n discovered Null's armor on the planet Nicht Ka. When he tried to take the armor's lightsaber, the suit seemed to awaken and clamped onto his wrist. When he finally managed to wrest the lightsaber free, the armor fell to the floor, releasing a cloud of bone dust. Cillmam'n unintentionally inhaled the dust and was subjected to visions of the past—memories of a warrior from the time of Adas, as well as Shas Dovos's creation of the armor, his corruption by the spirit protector, and his time as Warb Null. The dark side within the armor corrupted Cillmam'n, leading him to kill his companions and take the name Malleus.
The spirit protector initially appeared to Shas Dovos as a hovering gout of predominantly red flame, occasionally punctuated by violent flares of yellow ember. Later, it adopted the form of a recognizably near-Human figure, clad in long, flowing robes, with the hood pulled back to reveal an intense demeanor. Always translucent, the Spirit protector grew in size as it approached the young man, until it seemed to fill the entire room instead of simply moving closer. The protector only revealed the existence of its lore book to those it deemed worthy. Despite its initial contempt for the young man's arrogance, it chose to guide Shas Dovos, secretly increasing his power and knowledge without his awareness. The spirit exploited Dovos's metallurgical talents, subtly manipulating him into creating what it called "new skin." Even then, the spirit only revealed itself after Dovos had proven himself suitable for its purposes. Once visible, the spirit protector became extremely vocal and prone to fits of sinister laughter at the terror its presence caused Dovos.
The spirit protector's power allowed the compendium it was bound to to withstand the ravages of time. Without its influence, the book would have disintegrated centuries before Shas Dovos discovered it. Well-versed in Sith lore and magic, the spirit protector possessed all the book's secrets and refused to share them unless it deemed the potential recipient worthy. It foresaw Dovos's destiny as a champion in the quest to restore the Sith to galactic prominence and was also skilled in infusing inanimate objects with dark side energies, knowledge it imparted to Dovos. The protector could also permanently clad its apprentice in his magically empowered armor. The ancient Sith spirit could enter minds, influence dreams, and even compel beings to act. The spirit protector could change its size, shape, and appearance at will, manifesting as bursts of flame, blinding flashes of light, or humanoid and alien forms.
The spirit protector was first mentioned in Warb Null's entry in the Tales of the Jedi Companion, a sourcebook for Star Wars: The Roleplaying Game, published by West End Games in August 1996. The protector is only referred to as "spirit protector," "protector," or "Sith spirit," with no definitive specification of species other than "alien," and no gender or name. The spirit protector was later mentioned in the entry for Warb Null in the 2008 release of The Complete Star Wars Encyclopedia.
Edward M. Erdelac, a Star Wars author, noted on his personal blog that Warb Null's battle armor's design could be interpreted as an aesthetic reference to King Adas, an ancient Overlord of Korriban whose story was created by George R. Strayton and developed by Abel G. Peña. Erdelac theorizes that the spirit protector may have been the Overlord himself, which is why he included a vision of Adas in "Hammer," a short story in which a troubled Exploration Corps member discovers and dons Null's armor.