The Mask of Lord Momin was a helmet crafted and donned by the Sith Lord known as Darth Momin. The Jedi Order eventually seized it, placing it within their archives situated in the Jedi Temple located on Coruscant. Following the pursuit and demise of Chief Librarian Jocasta Nu, Darth Sidious claimed the mask for himself, subsequently bestowing it upon his Sith apprentice, Darth Vader. Ultimately, it found its place on the Imperialis.
The Mask of Lord Momin was a blue helmet forged by the Sith Lord and sculptor Darth Momin, utilizing his newly obtained lightsabers. It featured a prominent horizontal aperture, a central enclave linked to this opening, and a second vertical slit positioned on the elevated faceplate. Furthermore, the mask extended down to cover the neck with a small gorget. The mask also bore the marks of damage, exhibiting several cracks that traversed its surface.
When individuals were isolated with the mask in a confined space, they became vulnerable to the corrupting influence of the dark side of the Force. One method by which the mask could corrupt someone was through the appearance of two red, luminous eyes that emitted a flash of crimson light upon being gazed at. This corruption possessed sufficient strength to manipulate and control even decomposed bodies, with the mask's mere proximity being enough to exert its influence, without needing to be worn. The Mask of Lord Momin not only had the capabilities of corruption and control, but also the capacity for communication, as demonstrated when it conveyed its history to Darth Sidious to tell him. Once someone was possessed by the mask and wore it, their actions could be dictated by it, as seen with Lieutenant Roggo. Roggo, after being possessed, donned the mask, enabling him to design Fortress Vader, the castle of Darth Vader, in a matter of minutes.
From his youth, Momin produced creations considered by many to be abominable. Momin eventually channeled the Force into his creations, but ultimately he was imprisoned until Sith Lady Darth Shaa rescued him. Under Shaa’s guidance, Momin acquired considerable knowledge of the dark side of the Force, and eventually crafted his mask after intentionally disfiguring his own face. Eventually, Momin killed Shaa in a lightsaber duel, finding the term "apprentice" offensive. Perpetually wearing the mask, Momin journeyed to various Sith sites, seeking greater knowledge.
Subsequently, Momin commenced his latest endeavor. Utilizing resources inherited from Shaa, and with the aid of acolytes eager to assist his work, he engineered his own weapon: an engine capable of obliterating an entire city. Momin intended to infuse the Force into his engine at the moment of ignition, freezing the expressions of horror and agony on the faces of the city's inhabitants for eternity. However, when the Jedi located Momin, the presence of the light side of the Force disrupted his focus, causing him to lose control of the engine, resulting in his own demise. Only his mask remained, with his consciousness imprinted within it. One of Momin's creations was stored on Alderaan, though Momin's name was removed from its records.
Deemed a potent Sith artifact, the Jedi confiscated the mask and secured it within the Jedi Temple vaults. Accounts of Lord Momin and his activities were suppressed by both the Sith and the Jedi Order.
When Dooku and Sifo-Dyas were still initiates at the Jedi Temple on the Core World planet of Coruscant, the Mask of Lord Momin was housed in the Archive of Forbidden Artifacts, a Bogan Collection, alongside numerous Sith scrolls, the lightsaber of Darth Krall, and artifacts associated with the Sorcerers of Tund and the Yacombe. By 19 BBY, the Mask had been relocated to a different vault within the Temple, accompanied by other rare items such as a lightsaber rifle, a Sith holocron, another holocron, and a black starfighter.
Shortly after the creation of the Galactic Empire, Dark Lord of the Sith and Galactic Emperor Darth Sidious tasked his Sith apprentice, Darth Vader, with hunting and capturing Chief Librarian Jedi Master Jocasta Nu. Coincidentally, Master Nu arrived on Coruscant to acquire a memory crystal containing a list of Force-sensitive younglings to establish her school and rebuild the Order.
Upon arriving at the Jedi Temple and retrieving the crystal from the vault, she confronted the Grand Inquisitor in the Jedi Archives. When Darth Vader appeared, Nu fled to the Archive vault and employed the lightsaber rifle against him, ultimately blasting a hole through the temple wall and escaping outside. Nu was eventually apprehended and subsequently killed after informing Vader that Sidious intended to replace him, and that the list of younglings was his true objective.
Sometime after the confrontation, Sidious and a retinue of droids and Imperial Royal Guards were examining the collection of artifacts in the vault when Vader arrived, having survived several assassination attempts on himself. Sidious was holding and inspecting the Mask of Lord Momin as Vader inquired about the attempts.
By 18 BBY, the Jedi Temple had been transformed into the Imperial Palace, and the Mask of Lord Momin remained there, along with other artifacts. During Sidious's possession of the Mask of Lord Momin, the mask revealed its history and the story of Lord Momin to Sidious. Years after the establishment of the Empire, following a chase of two rogue Inquisitors, Sidious presented Vader with three gifts: the planet Mustafar to serve as Vader's personal stronghold, the Naboo Royal Starship as Vader's personal vessel, and the Mask of Lord Momin. Sidious believed that the mask would enable Vader to unlock the secrets within the Sith cave and grow stronger in the dark side of the Force during his mission to Mustafar.
The Mask of Lord Momin, along with Vader, architect Colonel Alva Brenne, and Lieutenant Roggo traveled to Mustafar aboard the Naboo Royal Starship. En route, Colonel Brenne examined the mask, contemplating Vader's architectural preferences. After a difficult landing on Mustafar, Vader meditated in the Sith cave while Colonel Brenne and Lieutenant Roggo developed plans for Fortress Vader. After Brenne presented Vader with an initial design that he rejected, Brenne returned to the Royal Starship but was killed. Vader, hearing Brenne's cries, entered the Royal Starship to discover Brenne's body and Roggo wearing the activated mask of Lord Momin.
Vader used his lightsaber to strike down Roggo. Shortly thereafter, a hologram activated, displaying a new design for Vader's fortress, which the mask had generated while corrupting Roggo. Using the Force, Vader retrieved the mask and brought it into the Sith cave, questioning its nature. The mask activated, and a pair of red eyes materialized, emitting a beam of red light at Vader, granting him a Force vision of Momin's past.
From that point, Momin revealed his past and attempted to possess Vader through the mask. The Sith Lord resisted, but upon exiting the cave, he encountered a Mustafarian scout party. Vader killed two of them, but used the mask to possess another, providing Momin with a physical body once more. As the last Mustafarian fled, Momin and Vader reentered the Sith Cave. In a brief exchange, Momin explained the purpose of Fortress Vader, describing it as a tuning fork for the Force, intended to open the gateway to the dark side. Vader allowed him to build it, but warned him of the consequences of betrayal.
Construction began on Momin's design. Once completed, Vader attempted to use the fortress to tune the Force energies of the Sith Cave and open the portal to the dark side. He failed, and the fortress was destroyed. Momin redesigned the fortress, and when it failed again, he repeated the process three more times. After the fifth failed fortress, Vader killed Momin's host and placed the mask on one of the Magma troopers at the construction site. Momin designed a sixth fortress, a seventh, and an eighth, each time with the mask possessing new hosts as Vader punished them with death.
When the ninth design was finished, Momin felt it was right, and Vader assured him there would be no tenth. When it proved capable of opening the door to the dark side, Vader was unwilling to wait any longer. However, the trial and error process of using the fortress designs had altered Mustafar's climate. Consequently, Vader was distracted by a Mustafarian uprising. Momin seized this opportunity to open the door to the dark side himself, resurrecting his original body. Momin's host handed the mask to its owner, and Momin killed them.
The Mustafarian army wiped out the Fortress Vader Imperial garrison and nearly killed Vader. Barely surviving, he returned to the fortress and tuned the Force from the Sith Cave to obliterate the Mustafarians. Once completed, Momin emerged and confronted Vader, challenging his beliefs about controlling the dark side, asserting that they must serve it. As he spoke, he severely injured Vader with his lightsabers and attempted to kill him. However, Vader rammed a large stone into him, crushing him against the wall. Momin died in disbelief, and his mask fell to the ground.
Vader returned the mask to Sidious, who decided to store it aboard his personal yacht, the Imperialis, alongside other rare artifacts. However, Momin's influence persisted within the helmet. During the Third Decennial Imperial Jubilee, the mask was on Alderaan. Stormtroopers Terex and Bil examined the manifest. As Terex departed, Bil looked at the mask and decided to try it on. Unfortunately, he became possessed by Momin's consciousness. Momin looked at the artwork on display for the Imperial Jubilee. When he found his artwork that did not have his name, Momin was angered by this and unleashed fury upon the Jubilee attendees. However, Commander Ellian Zahra killed Bil with her blade, and the mask deactivated. It was returned to the Imperialis after this incident.
When Lando Calrissian and his crew stole the ship, they discovered the helmet and the other artifacts. There, the helmet corrupted Aleksin to attack his brother, Pavol. Calrissian trapped the two inside the room and Pavol became corrupted as well. Calrissian was forced to abandon and destroy the Imperialis, destroying the mask.
The Mask of Lord Momin made its debut in the 2015 canon comic, Lando 3, authored by Charles Soule and illustrated by Alex Maleev. It wasn't until 2018, with the comic Darth Vader (2017) 21, also by Soule and illustrated by Giuseppe Camuncoli, that the mask received formal identification. In Star Wars: Crimson Reign issue four, the mask was once again seen under Vader's fortress, despite having been aboard the Imperialis in Star Wars: Lando. Soule clarified that this was not an error, as the "mask" depicted in Crimson Reign was merely a ghost that appeared to the Knights of Ren. When questioned about the ghost's apparent reaction to blaster bolts, he simply responded with "Yes," maintaining the ambiguity.