The Sith Warrior's story starts on Korriban. The warrior must partake in the trials to become a true Sith. It is revealed that the warrior was in fact, summoned to Korriban by an influential overseer named Tremel, also the headmaster of the Sith Academy. The warrior was brought to Korriban early from the training grounds for younger initiates on the planet of Ziost, but was taken to the former months ahead of schedule because of an enormous potential sensed by previous masters.
With Tremel as this warrior's new master, the latter engaged in many rigorous trials to prove themselves worthy of becoming a true Sith, such as finding an ancient warblade, defeating a vicious beast inside the tomb of Marka Ragnos, and sitting in the judgement of three prisoners at the academy. The Sith Warrior, after engaging in these activities, caught the attention of a visiting Sith Lord by the name of Darth Baras, who summoned the young warrior to his chambers for inspection. Baras, while being insulted by the low quality training the warrior had received under Tremel, recognizes the potential the warrior has hidden within, decides to spare the warrior his wrath, much to the dismay of Vemrin, an apprentice who had made himself a rival of the warrior ever since the latter landed on Korriban.
The final task Baras gives to the warrior: go into the tomb of Naga Sadow to find an ancient lightsaber. When this is completed, the warrior will finally have the title of Sith. For this task, Baras gave the hopeful a Twi'lek slave girl with knowledge of Korriban's tombs, Vette, who helps break into the tomb and retrieve the arcane weapon. The Sith Warrior is confronted by Vemrin in the tomb, as he coveted the blade for himself and the player's death. This resulted in a duel that ends in Vemrin's death. After returning to Baras, the warrior is made Baras' apprentice and tasked, along with Vette, to go by shuttle to the Imperial capital world of Dromund Kaas. The warrior obliges and meets the Sith Lord in the Dark Citadel of the Sith Emperor.
The Sith Warrior was then given several missions by Baras that involved infiltrating and assassinating many important political and military figures in the Empire. After helping their master interrogate a Republic spy, the Warrior was sent into the Dark Temple to retrieve an ancient torture device that would be beneficial to the inquisition. The spy, before dying, revealed information regarding an extremely gifted Jedi padawan being trained by one of Baras' oldest adversaries. Crucial information was being held by two of Baras' spies, contacts on the worlds of Balmorra and Nar Shaddaa. With this new information, the Warrior was dispatched to the planets to silence these two agents before the vital information slipped into the wrong hands.
Darth Baras discovers that a Jedi Padawan, under the guidance and protection of an old rival, Jedi Master Nomen Karr has been somehow able to discover elements of his spy network in the Republic. He sets the Sith Warrior on the task of first cleaning up the spy network, and then to seeking out and destroying the padawan.
To begin the task of cleaning up the network, Darth Baras send his new apprentice to Balmorra. On Balmorra, the Sith Warrior meets Malavai Quinn, an intelligence officer who will help with their mission. Their mission is to kill a Balmorran resistance general, Commander Rylon, who is really one of Darth Baras´s agents. The first task is taking down the general's son who is held in captivity by the resistance. The Warrior must fight the jailer and a squad of Republic troopers before they can get to the son. Then, the Sith Warrior must either wipe the son's memory or kills him.
Next, a similar cleanup is required on Nar Shaddaa. This time however, Darth Baras's burned agents have fallen under the protection of Lord Rathari, an upstart Sith Lord. The Dark Council has placed him in charge of their interests on Nar Shaddaa, so Darth Baras's apprentice must act without drawing unwanted attention.
With the primary cleanup handled, the Sith Warrior is sent on the trail of the Jedi Padawan. Intelligence has revealed that the padawan spent some time training on Tatooine. With local guidance from tracker Sharack Breev, the Sith Warriors follow the trail to Master Yonlach. Mastar Yonlach is a veteran of the Jedi Order and a great teacher. He was apparently able to bring out a special gift of the padawan, the ability to see the true nature of a person, be it Light or Dark. The Sith Warrior chooses (with relating dark or light side points) kill Master Yonlach or not-both strike the first emotional blow to the young padawan who had bonded with the Jedi Master.
Having discovered that the padawan was originally from Alderaan the Sith Warrior is directed to the planet and ordered to seek out and destroy any roots related to the padawan. The plan is to continue striking emotional blows to draw out the padawan so that she can be eliminated. The unscrupulous Duke Kendoh had been tasked by Darth Baras to uncover the padawan's connection on Alderaan. He leads the Sith Warrior to House Organa. This brings the Sith Warrior into a confrontation with General Gesselle Organa. From her, the padawan's identity, Jaesa Willsaam, is learned as well as the whereabout of her parents.
After confronting Jaesa's parents, the padawan is finally drawn out. She secretly contacts the Sith Warrior and schedules a rendezvous in the Distant Outer Rim. The meeting, however, doesn't go as planned. Master Nomen Karr having discovered the planned meeting, instead sets a couple of Jedi in ambush. After dispatching the Jedi (again with a light/dark side of the force choices about both if to fight them at all and if to kill one or both of them), a distraught Jaesa again contacts the Sith Warrior, pleading for an end to his chase. At the same time, Master Nomen Karr contacts Darth Baras, calling him out to settle it between themselves.
Darth Baras sends the Sith Warrior in his place to Nomen Karr's hideout on Hutta. Finally, the Sith Warrior removes the last emotional support Jaesa had left. Rather than destroy Jaesa, the Sith Warrior takes advantage of Jaesa's fragile state to sway her to join him. This marks be beginning of a subplot to either to break Jaesa and turn her to the dark side or to recruit her-and join the Warrior if he or she is-as a Sith with secret leanings for the light side. Darth Baras upon discovering is surprised, but as a result of the turn of events bestows on the Sith Warrior the title of Lord.
After a brief break, to enjoy being given the title Sith Lord, Darth Baras sends the Sith Warrior back to Nar Shaddaa. Darth Baras's master on the Dark Council, Darth Vengean is looking for a way to break the truce between the Republic and the Empire and bring the two back into a full-fledged war. A Republic general is meeting with some Empire traitors on Nar Shaddaa, and Darth Baras feels that killing the general might be the key.
Upon successfully eliminating General Karastace Gonn, Darth Baras is given the go ahead to begin Plan Zero, which involves eliminating all the top leaders of the Republic military. Darth Baras has six targets in mind. Four of the targets are on Taris. While Darth Baras tracks the location of the final two, he sends the Sith Warrior to eliminate the targets on Taris.
On Taris, Warrior meets Moff Hurdenn, who quickly assigns Lieutenant Pierce to assisting his task. Lieutenant Pierce will provide intel from the Command Center while Warrior working on the targets. Your told these four generals make up the Republic War Trust. The War Trust are four Republic generals that rarely are in one place. One by one, Warrior eliminates them and in the end Lieutenant Pierce is assigned permanently to Warrior's service.
With the War Trust eliminated, Plan Zero was well underway. Baras had tracked down Warrior's next target in Quesh orbit, Admiral Monk from Republic fleet. Warrior pursues the admiral inside Darth Vengean's flagship, but has to follow him to the Quesh surface. In there admiral reveals to the Warrior that he was actually one of Baras' spies. This distraughts the Warrior but he keeps serving Baras.
Warrior's final target is Jedi Master Xerender, currently located in the frozen wastes of Hoth. Because Xerender had enlisted the aid of local Talz, Warrior soon finds himself tracking down same targets along with a bloodthirsty Talz named Broonmark. Their first meeting isn't warm but eventually they decide cooperate. Eventually Warrior learns Xerender's goal on Hoth: to awaken a long forgotten Jedi Master Wyellett from ice. Baras knows Wyellett from a long time ago, because they fought once and Wyellett defeated him and tried to turn Baras to light side, which he refused. Now Warrior has to eliminate both Xerender and Wyellett. He finds them both inside the wreck of the Star of Coruscant and with Broonmarks help, he defeats them both. With targets dead, Plan Zero is complete.
Warrior returns to Dromund Kaas to be congratulated by Baras. Baras then reveals that starting the war with the Republic again was not the only goal of the Plan Zero, but it would also serve as method for him to ascend to the Dark Council. The only thing standing in his way was Baras' superior, Darth Vengean, Baras offers Warrior an opportunity to kill Vengean and then take a rightful place as Baras' right hand. Warrior agrees and Baras orders Warrior to rescue Vengean's former apprentice, Lord Draagh, so that they can destroy Vengean together. Warrior succeeds in freeing Draagh and together they defeat Vengean, allowing Baras to ascend to the Dark Council
After ascending to the Dark Council, Baras gives the Warrior a new task: to destroy a Republic plan to thwart Imperial mining oprations on Quesh. Warrior travels to Quesh and encounters Republic forces. It seems that the Warrior arrived too late, because the bomb they set is ready to blow. However, their remote detonator doesn't work and Warrior quickly eliminates the Republic forces. Warrior is then contacted by Lord Draagh, who first congratulates Warrior for a job well done, but then reveals that their detonator didn't work because it was changed to a wrong one. The right one was currently in Draagh's hand and he was set to blow the bomb. The Warrior asks him who gave him the order to kill him/her, and Draagh reveals that it was Darth Baras. The Warrior swears revenge, but then Draagh sets off the bomb. Warrior barely survives, but Baras and Draagh believe him to be dead.
As the Warrior struggles in the edge of consciousness, he faintly sees two shady figures in front of him/her, talking about him/her. They say that if /she is the right one, s/he will make it on his own. Later, Warrior awakens and follows the figures trail to an Imperial outpost. In there the Warrior meets the figures who reveal themselves to be the Emperor's Servants One and Two, the Emperor's Hand. They tell the Warrior that the Emperor himself has chosen him/her to become the Emperor's Wrath, the Emperor's personal enforcer. Warrior gladly accepts, because it also gives him/her an opportunity to face Baras. The Hand then tells the Wrath that when Baras rose to the Dark Council, he made a false claim that he is the Voice of the Emperor, a person whom through the Emperor speaks. All the members of the Council had accepted this claim, save one, Darth Vowrawn. The Hand explains that Vowrawn's survival is paramount as well as weakening of Baras' position. To this end, the Hand sends Wrath to oversee this to happen. Wrath's first task is on Belsavis.
The Republic prison planet Belsavis had become a target of personal interest to Baras because he had learned that the Republic imprisoned his own sister, Darth Ekkage, there. Wrath's task was simple: eliminate Darth Ekkage. However, the Hand didn't know where Ekkage was being held, so Wrath had to track down a Baras' rescue party led by a Sith Lord in order to find her. While tracking down the party, Wrath encountered a Jedi Knight who too was looking for Ekkage. Although Wrath was suspicious about this, he had no choice but to cooperate with the Jedi. The Jedi suggested that they also eliminate Ekkage's followers who too were imprisoned along with her. Wrath agreed. Finally they eliminated all the followers and found Ekkage's holding chamber and the Sith Lord who led the rescue party. Ekkage was thrilled to return to Baras, but Wrath and the Jedi defeated her and the Sith Lord. Ekkage's death will certainly infuriate Baras and weaken his position. Wrath and the Jedi parted ways (or Wrath kills the Jedi), and he returned to his ship for more instructions from the Emperor.
The Hand congratulated Wrath of his success, but there was no time to rest. Wrath's next task was to go to Hoth and ensure that the Empire's elite Armageddon Battalion is transferred from their worthless position on Hoth to the main battlefront on Corellia. Baras had sent the Battalion to Hoth in order to discredit Darth Vowrawn. Wrath was able to "persuade" the battalion to leave for Corellia. While on Hoth space station with the intention of leaving, Wrath encountered Baras' new apprentice, Lord Draagh. Draagh had knocked out Wrath's entire crew and was all set to kill him/her, but not before mentioning that Baras had sensed his sisters death and learned from that that his old apprentice was still alive. Wrath and Draagh fought a fierce battle, but eventually Wrath was able to push Draagh to the bottom of the catwalk in which they were fighting. The whole place was on fire and Draagh was burned alive.
Wrath returned to his ship and the Hand was troubled that Baras now knew that s/he had survived. Now it was all the more important to stop Baras fast. The Hand knew that Baras will be taken down on Corellia, but before that Wrath had important mission to take care of in the mysterious planet of Voss. According to the Hand the real Voice of the Emperor had traveled to Voss and had gone missing there. It was up to Wrath fo find him and make sure Baras doesn't get the chance to eliminate him, as Baras too had laid his eyes on Voss.
To start his search, Wrath first had to make contact with a Voss Mystic whom The Voice had last time seen with. Wrath met the Mystic and he said that in order to find him, Wrath needs to find an amulet that belonged to the Mystic. Part of it was left in the Shrine of Healing while another part was with some Voss commandos in the Gormak Lands. Eventually Wrath managed to obtain the amulet and the Mystic revealed that the Voice had traveled to the Dark Heart in the Nightmare Lands. Wrath journeyd there and found the Voice. At that point the Voice was a Voss too, but as it was, he spoke with the Emperor's voice. Wrath kneeled before him, and the Emperor was pleased that s/he made it. Then he said that this Voice must be destroyed, and that only Wrath can do it. Wrath fought fiercely and destroyed the Voice. Before the Emperor left from the body, he was extremely pleased that his Wrath had performed admirably. Wrath then returned to his ship, but then s/he received a warning from the Mystic. He had seen a vision in which one of Wrath's followers will try to betray him/her. Wrath took this warning seriously.
The Hand then urged Wrath to travel to Corellia to strike the final blows against Baras. But before s/he could set out, Malavai Quinn said that Baras had set up a new type of sensor net, that automatically sends a destroying signal to Imperial fleet if a ship entering the system is not authorized to enter. To get through, Wrath first needed proper codes. Malavai learned of an Imperial dreadnaught near Voss that had the needed codes. Wrath and Malavai traveled to the ship. When they arrived Malavai revealed that the sensor net was only a ruse, so that he could lure Wrath into a trap he had set up. The reason Malavai did this was because his only real master was Darth Baras. Malavai brought in droids to destroy Wrath. Unfortunately for him, Wrath defeated the droids easily, and Malavai realized his mistake. Malavai expected the Wrath to kill him, but Wrath spared him and said that he will be okay if he stays loyal to Wrath from now on. Malavai accepted the offer and they resumed course to Corellia.
Baras' main goal on Corellia was to kill Darth Vowrawn. The Hand had learned that Baras had sent three assassins to kill him along with one exceptional, who was not yet in the system. Wrath had to eliminate these assassins to ensure Vowrawn's survival. S/he was able to kill two assassins, but third managed to slip through. S/he had no other choice but to race into Vowrawn's headquarters and warn him of the impending danger. However, Vowrawn had learned of Baras' assassination attempt on him, and he and his guards mistook Wrath as the assassin. Wrath had to get to Vowrawn even if he has to kill all of his guards. S/he finally reached Vowrawn and tried to explain that he came to protect him, but Vowrawn didn't listen. He ordered his guards to kill the Wrath. That's when the assassin made his move, but Wrath's reflexes were faster and s/he was able to save Vowrawn from him. Vowrawn then apologized Wrath for misunderstanding. Wrath suggested that Vowrawn evacuate himself to Wrath's ship and assured that his crew will keep him safe. Vowrawn accepted and informed Wrath what he should do to cripple Baras here. Baras had spies inside the enemy. First eliminate them. After dispatching them Wrath's ship was attacked by the exceptional assassin. Wrath's crew wasn't able to defeat him, but at least they managed to get Vowrawn out unharmed. Wrath went to meet with Vowrawn. He then revealed the most critical instrument to Baras' plans: a Sith being known only as The Entity. Baras had been using it for years for his plans, and if he should lose it, he would be finished. Vowrawn knew a ritual to free it. Together they traveled to Baras' base and found The Entity. But they were being followed by the last assassin, who, to Wrath's surprise, was revived and cybernetically enhanced Lord Draagh. Draagh not only wanted to kill Vowrawn but also get revenge on Wrath. Wrath and Draagh fought once again, and although Draagh had become more powerful, he was no match to The Emperor's Wrath. Wrath killed him and Vowrawn released The Entity. With Baras' plans on Corellia thrown into disarray, the only thing that was left was to deal with Baras in person. Vowrawn figured that he will attempt to hold on to his false claim as the Voice of the Emperor in front of the Dark Council. This gave Wrath an excellent opportunity to prove his claims to be false and destroy him.
Wrath traveled to Korriban and Vowrawn made certain that s/he will be brought in front of the Council. As Vowrawn expected, Baras still hold on to his false claim. Vowrawn introduced the newest arrival and Darth Marr demanded to know who s/he is. Wrath then claimed that he is The Emperor's Wrath. Baras laughed at that claim, but Marr decided that Wrath and Baras duel, and the victor will officially receive his claim as true. The duel was long and fierce and Baras taunted Wrath every now and then, but eventually Wrath managed to defeat him. In his weakened state, he demanded that the Council destroy Wrath and give him what he is, but the Council was now convinced that Baras was not the Voice of the Emperor. Depending on conversation choices, Wrath can either kill Baras, or he will be expelled from the Council and imprisoned. Finally, the entire Dark Council rose and bowed to the one and only Emperor's Wrath.