Darth Mortis, a Human male, achieved the title of Dark Lord of the Sith and held a position on the governing Dark Council of the reconstituted Sith Empire during the period of the Cold War with the Galactic Republic. As one of the twelve Dark Lords seated on the Council, Mortis was in charge of the Sphere of Laws and Justice. He mentored at least one Sith apprentice, named Zavrasha, and was dedicated to upholding the Treaty of Coruscant. As the Galactic War with the Republic progressed and the Council's membership dwindled, he took on a leadership role alongside Darth Marr and Darth Ravage.
By the time the Cold War began with the Galactic Republic, Darth Mortis, a Human male, had ascended to the rank of Sith Lord within the resurgent Empire. His considerable power earned him a seat on the ruling Dark Council of the Empire, and as one of the twelve Dark Lords of the Sith he controlled a specific Sphere of Influence within the Empire: the Sphere of Laws and Justice. As the Sphere's leader, Mortis was responsible for overseeing the Imperial justice system and the Empire's law enforcement branches. Towards the end of the Cold War, Mortis began training a Sith apprentice named Zavrasha, whom he dispatched to the neutral moon of Nar Shaddaa to ensure that Admiral Jefand Ange's activities there did not threaten the peace established by the Treaty of Coruscant. Darth Gravus, the Sith Lord in charge of the invasion of Taris, was a political ally of Mortis.
When the Galactic War erupted with the Republic, Darth Baras, a fellow Councilor, summoned Darth Mortis and the other Council members to their meeting chamber on Korriban. Due to their oversight of the Battle of Corellia, Darth Decimus, Hadra, and Acharon attended the meeting through hologram. Darths Marr and Ravage were physically present on Korriban with Mortis as Baras attempted to proclaim himself the Voice of the Emperor—the public representative of the Sith Emperor's will and, consequently, the ruler of the entire Empire. However, Darth Vowrawn and Baras' former apprentice interrupted Baras. The Sith Warrior, who had been appointed as the Emperor's Wrath after Baras' betrayal, battled the false Voice in front of the Council.
After the Wrath killed Baras, Darth Vowrawn guided Mortis and the others to acknowledge the Emperor's support for the warrior, accepting that the Wrath was not bound by the Council's desires. When the Wrath left, Darth Thanaton presented his own issue to the Council: the head of the Sphere of Ancient Knowledge was engaged in a Kaggath, an ancient Sith ritual duel, against his subordinate Lord Kallig. After Kallig bested him on Corellia, Thanaton asked Mortis, Ravage, Vowrawn, and Marr to eliminate the upstart slave, but the other Councilors declined to interfere when Kallig arrived to continue their battle. Once Kallig defeated Thanaton and forced his submission, Mortis rose and apologized to his fellow Councilor before killing him with the Force. Acknowledging Kallig as the victor, the four Dark Councilors rewarded the young Sith Lord with Thanaton's vacant seat, dismissing Darth Nox's question about when the Emperor would meet with the Council. As the Council adjourned, Mortis advised Nox to return to Dromund Kaas and secure the loyalty of their followers, promising to summon Nox when the Dark Council next convened.
Following the Republic's victory in the Battle of Corellia and the deaths of Decimus, Hadra, and Acharon, the Dark Council was angered to learn that Darth Malgus had proclaimed his own empire on the planet Ilum. This new empire did not discriminate against alien species and was not subject to the political conflicts plaguing the current Empire. Mortis, along with Marr and Ravage, assumed a leadership role on the Council, dispatching Grand Moff Ilyan Regus and Darth Arho, Baras's successor as head of the Sphere of Military Offense, to lead the campaign against Malgus and the Republic on Ilum. Later, Mortis and the other Councilors met in their chambers beneath the Imperial Citadel on Dromund Kaas, the capital, to discuss who would succeed Darth Hadra as the head of the Sphere of Technology. Mortis was among those who opposed Darth Marr's candidate, the Falleen Darth Karrid. Mortis believed that the Empire was wrong to adopt Malgus' policy of allowing aliens to join their ranks, and he proposed the Human traditionalist Darth Gravus as an alternative to Karrid. He attempted to persuade the Council to grant Gravus a seat once he reclaimed the mineral-rich world of Leritor. After Karrid eliminated Gravus, Mortis shifted his support to Karrid, admitting that he had underestimated her.
During the Hutt Cartel's invasion of Makeb, Darth Mortis summoned an Imperial individual to help him against The Shroud, a spy planning a rogue attack on Dromund Kaas. The Dark Councilor introduced Evie Bo, the former top lieutenant of The Shroud, to the Imperial individual, who provided microbinoculars to locate another lieutenant in the city and stop The Shroud. After neutralizing the Shroud's lieutenant, the Imperial individual traveled across the galaxy to uncover the Shroud's plan. The trail led to Nar Shaddaa, where Bo and the Imperial individual discovered the Shroud's plan to launch a ship through hyperspace into Kaas City. The Imperial individual thwarted the attack and seemingly killed the Shroud. However, upon returning to Dromund Kaas, the Shroud hijacked Mortis' holofrequency, revealing that a double had been killed in his place. Before signing off, the Shroud activated a neural scrambler in Bo's brain using a trigger phrase, erasing her memory. As Mortis intervened, the individual convinced an amnesiac Bo that she was a servant of the Empire.
In 3636 BBY, the Eternal Empire of Zakuul invaded the galaxy, and Darth Marr was one of the first victims of the Eternal Empire conquest. The Eternal Fleet blockaded Dromund Kaas before the year's end, and the Dark Council members fiercely resisted the invasion led by Zakuulan Emperor Arcann, but they were defeated. The surviving Council members went into hiding to avoid destruction, leaving Darth Acina as the only remaining Dark Councilor in the public eye, who proclaimed herself Empress of the Sith without opposition. Acina signed a peace treaty with Zakuul and ruled with public support for the next six years. Around 3630 BBY, the Eternal Alliance, formed by former Sith Intelligence Minister Lana Beniko, defeated Zakuul's Empire. The surviving members of the former Dark Council, including Vowrawn, Ravage, and Mortis, began to resurface.
After defeating Zakuul, the Commander of the Eternal Alliance seized the Eternal Throne and gained control of the massive Eternal Fleet. Instead of using it to conquer the galaxy, the Commander declared an era of peace and sought to gain new allies through diplomacy. Disgusted by what he perceived as the Commander's weakness and Lana Beniko's betrayal of the Sith Empire in favor of the Eternal Alliance, Mortis was willing to see the Eternal Fleet destroyed rather than allow those he deemed unworthy to possess it. He joined the Order of Zildrog, a secret group formed by former Horizon Guard Vinn Atrius dedicated to killing the Outlander and destroying the Eternal Alliance. Persuading Vinn Atrius with his desire for revenge, Mortis traveled with the Order to Nathema, where GEMINI 16 found and planned to awaken Zildrog, an ancient Iokath superweapon. However, the GEMINI droid deceived and betrayed many of her allies, trapping them in energy transfer chambers to fuel Zildrog's awakening. Darth Mortis was among those drained to awaken Zildrog. The Alliance Commander, along with Lana Beniko and Theron Shan, arrived shortly after and destroyed the mechanical entity, causing the entire chamber housing it and the GEMINI's victims to explode.
Mortis, a Human male with orange eyes, pale skin, and black hair, was one of the older members of the Council by the end of the Cold War. While he did not strongly adhere to Sith traditions, he supported the Empire's anti-alien policies, which led him to favor Darth Gravus over Darth Karrid when the Dark Council considered replacements for Darth Hadra. However, he changed his mind when Karrid outmaneuvered and killed Gravus, realizing he had underestimated her.
Darth Mortis was a powerful practitioner of the dark side of the Force and a master of both telekinesis and lightsaber combat.
Darth Mortis is a character featured in Star Wars: The Old Republic, a massively multiplayer online role-playing game created by BioWare and LucasArts. He initially appeared during the final missions of the Sith Warrior and Sith Inquisitor's class storylines on Korriban. Following the game's release, he was also highlighted in the 2012 reference book Star Wars: The Old Republic Encyclopedia, which identified him as the head of the Sphere of Laws and Justice, and he was a character in The Old Republic: Annihilation, a novel by Drew Karpyshyn set after the events of the Battle of Ilum. In the 2013 Rise of the Hutt Cartel expansion, Mortis plays a crucial role in the the Shroud-related macrobinoculars storyline, available to all Imperial classes.
Knights of the Fallen Empire established that all Dark Council members, with the exception of Darth Acina, perished or vanished during the Eternal Empire conquest. However, Mortis is later revealed to have survived and reappears during "The Nathema Conspiracy" flashpoint. His presence is contingent on the player's Light Side choice to address the galaxy as a peacekeeper at the conclusion of Knights of the Eternal Throne, regardless of their class. If the player chooses the Dark Side path, becoming a new Emperor and using the Eternal Fleet for personal power, Mortis has no reason to oppose them, and Indo Zal takes his place as Zildrog's victim.