Darth Acina, a Human female Dark Lord of the Sith, held the position of Sith Empress and governed the re-established Sith Empire. Before ascending to the throne, she served on the Dark Council and oversaw the Sphere of Technology.
During her time as ruler, the Sith Empire engaged in war with the Eternal Empire originating from Zakuul. Shortly after the fall of Zakuul, she perished due to an Iokath superweapon that she had intended to secure for the Empire. Darth Vowrawn then took over as her successor.

Acina's initial Sith training took place at the Sith Academy located on Korriban. As a Sith apprentice, some of her earliest tasks involved eliminating local pests within the tombs of the Valley of the Dark Lords. Ultimately, she achieved the rank of Dark Lord of the Sith. Following the demise of Darth Karrid near Duro in 3640 BBY, the Emperor's Hand selected Acina to lead the Sphere of Technology and oversee the Arcanum, a repository of potent technology. Her position on the Dark Council was solid during this period, as she regulated access to the Arcanum, compelling fellow Councillors to seek her favor. However, one of her trainees secretly pledged allegiance to the Dread Masters, enabling their follower, Tagriss, to orchestrate a Raid on the Arcanum and abscond with numerous perilous artifacts, including the Darkstaff and the Seeds of Rage. With her standing threatened, Acina swiftly sought assistance from an Imperial individual to locate and retrieve the Seeds. After successfully recovering the final Seeds on Ilum, the Imperial returned them to Acina, who intended to conceal them on Ziost.

In 3636 BBY, the Eternal Empire of Zakuul made its presence known to the wider galaxy and initiated the Eternal Empire conquest against both the Empire and the Republic. Within a year, Dromund Kaas was under blockade, and the majority of Dark Council members either perished or vanished amid the turmoil. Darth Acina was among the first to realize the Sith's disadvantage and, along with Darth Vowrawn, remained on the Dark Council when the Zakuul–Imperial treaty was brokered by the Minister of Logistics. Capitalizing on the power vacuum, Darth Acina seized leadership of the Empire, proclaimed herself Empress of the Sith, and pledged loyalty to Emperor Arcann of the Eternal Empire, who publicly recognized her claim.

For the subsequent five years, Acina governed the Sith Empire, enjoying widespread support from the populace. As Empress, she strategically waited during Arcann's reign. However, following his defeat by the Outlander in the Battle of Odessen, she recognized an opportunity to restore the Sith Empire's dominance. Acknowledging that the Alliance that had triumphed over Arcann possessed the strength to eventually overcome his notoriously unpredictable sister, Vaylin, she openly defied her heralds, bringing an end to the era of Sith submission. When Vaylin's Eternal Fleet launched an Invasion of Voss, Acina dispatched the Imperial fleet to aid the Alliance and its Commander in battle. The timing of the Imperial fleet's arrival proved crucial, as it successfully drove away the Eternal Fleet, decisively ending the conflict. In the aftermath, Acina recognized the Alliance as an independent power and invited the Alliance Commander to Dromund Kaas to discuss a potential agreement.

Upon the Alliance Commander's arrival on Dromund Kaas, Acina tasked the current Minister of Logistics, Gelmid Lorman, with escorting her guest from the spaceport. After the Alliance Commander, accompanied by advisors Lana Beniko and Theron Shan, were brought to Acina's chambers, the Empress proposed a private discussion regarding their alliance aboard her personal shuttle. In flight and away from eavesdroppers, Acina assured the Commander of her genuine intentions and that she had no desire to seize the Eternal Throne for herself. Their conversation was disrupted by a sudden engine malfunction, forcing Acina to crash-land the shuttle and evacuate. Stranded in the Dromund Kaas wilderness, Empress Acina and the Commander had to contend with the planet's dangerous wildlife and lightning storms. The pair eventually discovered that the GenoHaradan, whom the Empress had always considered a myth, had sabotaged their shuttle. However, these legendary assassins proved no match for the Alliance Commander and the Empress of the Sith, who quickly dealt with them and located their camp. The Commander uncovered logs in the camp revealing that Leontyne Saresh, the former Supreme Chancellor of the Republic, had orchestrated the assassination attempt in an effort to take control of the Alliance.

Under intense fire, Empress Acina and the Commander sought refuge in a nearby Sith tomb. As they ventured deeper into the tomb, they encountered the treacherous Minister Lorman, who was responsible for the shuttle sabotage, along with a GenoHaradan strike team determined to complete their mission. After eliminating the GenoHaradan, Acina allowed the Alliance Commander to decide Lorman's fate. Following the Alliance Commander's return to their headquarters on Odessen and confrontation with Saresh, Acina contacted the Commander again to formally propose an alliance. Shortly thereafter, she pardoned the Imperial officer Malavai Quinn, who had been imprisoned by former Minister Lorman for insubordination, and appointed him as her advisor.

The Commander's Alliance proceeded to wage war against Vaylin, ultimately defeating her. Unfortunately, this left the Eternal Throne vacant, causing the GEMINI captains to revert to their default programming and order the Eternal Fleet to indiscriminately bombard populated worlds. Acina issued an urgent distress signal to the Alliance, who subsequently claimed the Eternal Throne and assumed control of the Eternal Fleet. Aware of the immense power now wielded by the Eternal Alliance, Empress Acina began preparing her people for war, even as cleanup efforts continued on Dromund Kaas following the recent Eternal Fleet bombardment.
Upon receiving anonymous intelligence about a remarkably powerful superweapon on the recently rediscovered world of Iokath, Acina dispatched a contingent of Imperial forces to secure it. On Iokath, the Imperials encountered Republic forces pursuing the same objective and were soon joined by the Eternal Alliance's Eternal Fleet. Acina sent Major Quinn as an ambassador to the Alliance Commander, instructing him to sabotage the meeting and escape if the Alliance turned against the Empire. The Empress herself made a holocall, formally requesting the Commander to side with the Empire against the Republic forces led by Supreme Commander Jace Malcom.

When the Alliance Commander sided with the Republic, Acina launched an assault against both the Republic and the Alliance. Later, she discovered a hidden access point to the superweapon and attempted to activate it, unaware of the danger it posed. Upon being confronted, Acina mocked the Commander about the superweapon and sat on an Iokathi throne, which rejected her and inflicted a mortal wound. With her final words, Acina apologized to the Commander for her error, claiming that nothing could halt the awakened Six Gods, before passing away. Darth Vowrawn succeeded her as the Emperor of the Sith Empire.

Acina was known as a progressive and pragmatic Sith, who was difficult to impress as a Dark Council member. Conversations with her were often compared to a stimulating guessing game. Following the death of Darth Marr, she sought to unify the remaining elements of the Sith Empire. During the Eternal Empire's assault on Sith space, she avoided the other Dark Councilors' attempts to directly confront the new enemy, a choice that ultimately left her as the sole survivor. With no opposition and having avoided direct involvement in the Sith's surrender to Zakuul, Acina easily claimed the throne for herself, garnering unexpected popular support. While she could easily be labeled as a cowardly opportunist, many recognized that Acina's more measured and calculated approach allowed her to achieve greater heights than anyone anticipated, leading some to call her the "wisest of the Sith".
Even during her time as Empress, Acina typically stayed up late and rose early, rarely receiving visitors. She diligently practiced lightsaber techniques and consumed only purified water from Dromund Kaas. Surprisingly, for the head of the Sphere of Technology, Acina enjoyed horticulture as a hobby. In her interactions with the Outlander, Empress Acina demonstrated a willingness to collaborate against Zakuul, proving to be a dependable ally both during their personal encounters and their subsequent battles against the Eternal Throne. Nevertheless, she remained as ruthless as any Sith, readily prepared to execute Minister Gelmid Lorman for his betrayal during the revolt against the Eternal Empire.

As expected of the leader of the Sphere of Technology, Acina possessed technical expertise rarely seen among other Sith Lords. Despite this, Darth Acina seemed to avoid the cybernetic enhancements that many of her peers and subordinates relied on, although she may have simply not sustained any injuries that would have necessitated them. She was a skilled pilot, even using relevant jargon when faced with an emergency.
As a member of the Dark Council, Darth Acina was strong in the Force and competent in combat. However, during her initial tenure on the Council, she was a relatively minor figure and appeared to defer to Darth Marr's leadership alliance. She wielded a purple double-bladed lightsaber in combat, though as Empress, she lamented the limited opportunities she had to use it personally.
Darth Acina made her debut in Star Wars: The Old Republic: Rise of the Hutt Cartel, the first Digital Expansion for the BioWare video game Star Wars: The Old Republic. Her Codex entry initially stated that she succeeded Darth Hadra, who had been killed on Corellia. However, this contradicted the 2012 novel The Old Republic: Annihilation, which stated that Darth Karrid was Hadra's successor. This discrepancy was recognized as an error, and the Codex entry was corrected in Update 2.1.1 to accurately state that Acina succeeded Karrid. Rosalind Ayres provided the voice for Acina. Darth Acina's original character model was a generic human female, but she received an updated model with a unique face and armor as Empress in Knights of the Eternal Throne.

Player characters, regardless of gender or faction, can attempt to engage in romantic interactions with Acina throughout various storylines in Star Wars: The Old Republic. During the opening and closing conversations in the "Seeds of Rage" storyline, Imperial-aligned players have the option to compliment Acina on her appearance. She seems flattered, but redirects the conversation back to the mission at hand on both occasions.
During Chapter II: Run for the Shadows of Knights of the Eternal Throne, players of any gender and faction can try to flirt with Acina while inside the Imperial Citadel and when stranded alone with her in the jungles of Dromund Kaas. Acina is flattered and expresses interest in the possibility of a romance, but declines the offer due to propriety.
Final attempts to initiate a romantic relationship with Acina can be made during the Iokath storyline, which is available to Imperial players only. Acina rejects the offer once more, asserting that the ongoing battle takes precedence. However, she hints that she might reconsider the offer after the conflict is resolved.
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In _Star Wars: The Old Republic: Knights of the Fallen Empire _ Chapter XV: The GEMINI Deception , if the Outlander rescues Zasha Ranken , the latter informs Empress Acina, who expresses her gratitude via e-mail, despite being unable to openly support the Alliance .
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When conversing with Acina after the events on Voss, if the player completed her mission involving the Seeds of Rage in the past, she will greet the Commander as an old acquaintance rather than a stranger. She will also acknowledge Darth Nox as a former fellow Dark Council member if the player is a Sith Inquisitor .
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During the events on Iokath, the player must choose between aligning with the Republic or the Empire, neither of which is a light side or dark side option. This decision significantly impacts the fates of both Acina and Malcom, with them mirroring each other's role as either an ally to the Eternal Alliance or someone who seeks to activate the superweapon.

If the player sides with the Empire, the Republic launches a counter-offensive against the Imperial base on Iokath. Acina meets with the Commander after the initial attack is repelled, and they agree to retrieve weapons from an Iokath weapons cache to gain an advantage over the Republic. As Supreme Commander Malcom threatens to activate a superweapon capable of eradicating all life on Iokath, Acina provides the Commander with a walker called Crimson Talon to storm the Republic base and stop Malcom. Despite the Commander and Theron Shan's attempts to dissuade him, Malcom activates the superweapon, awakening the Six Gods, which results in his death. Despite being leaderless, Republic forces continue to resist, and Acina assures the Commander that their future partnership will remain strong.
Acina appears during the story for Imperial players only after Iokath.
Acina reappears on Ossus at the conclusion of the Jedi Under Siege storyline, regardless of whether players remain loyal to the Empire or become double agents for the Republic. Malgus informs Acina about either the capture or death of Gnost-Dural and how it will benefit their cause. Acina then comments on either the Commander's successful acquisition of the farmer's data (loyalist) or the loss of the data and its impact on the Empire in the renewed war (saboteur).
Darth Rivix will brief Acina on the whereabouts of Darth Malgus following the Commander's mission to the Dantooine Jedi Enclave.
After Malgus is defeated on Elom, Acina arrives to assist in restraining him with the Force and placing him under arrest.