Darsin was a male Human who served as the apprentice of the Sith Lord Darth Rivan during the New Sith Wars. He resided in Rivan's Sith fortress on the planet Almas, where his master subjected him to experiments and dark side rituals. Darsin eventually came close to attaining the rank of Dark Lord of the Sith and planned to assume the name Darth Malus, but before he could become a Sith Lord, he died as a result of Rivan's alchemical manipulations. Darsin's consciousness survived as an incorporeal Sith spirit, and Rivan bound him to act as a guardian of the Sith fortress. Centuries later, in about 20 BBY, the Chevin slaver Phylus Mon, the Human Dark Jedi Karae Nalvas and several of their minions ventured into the Sith fortress in search of the secrets of the creation of Sith battlelords, a class of warrior developed by Rivan, and their incursion caused Darsin to re-awaken. The Sith spirit attacked the interlopers, but was warded off by the power of the Darkstaff, a Sith artifact that was carried by Mon. Shortly thereafter, Darsin ambushed a band of freelance agents who had ventured into the fortress in the wake of Phlyus Mon's intrusion, and he was defeated by them.
Darsin was a Force-sensitive male Human who lived during the era of the New Sith Wars. At some point between about 1417 BBY and 1167 BBY, Darsin became the apprentice of the Dark Lord of the Sith Darth Rivan and studied the ways of the dark side of the Force. He lived with Rivan inside the Sith Lord's fortress on the planet Almas in the Cularin system, and there, the Dark Lord subjected Darsin to dark side rituals and performed alchemical experiments on him, treating Darsin as little more than a slave. To reflect Darsin's lowly position, a small, uncomfortable lump of rough granite was installed inside the fortress next to Rivan's throne, for Darsin to sit on and meditate.
Darsin eventually betrayed Darth Rivan and came close to becoming a Dark Lord of the Sith. He planned to assume the honorific "Darth" and rename himself "Darth Malus" on usurping Rivan's position, but before he could ascend to the rank of Sith Lord, Darsin died as a result of the damage that had been done to his body by Rivan's experiments. His corpse was interred inside a black marble sarcophagus in a specially constructed crypt that had been built for Darsin and Rivan in the depths of the Almas fortress, but Darsin's consciousness lived on as an incorporeal Sith spirit. Through the Force, Rivan bound his former apprentice to the dark side presence that permeated the fortress, and Darsin was compelled to act as a guardian of the stronghold and attack intruders.
Rivan was later driven away from Almas by the Jedi Order, and the Sith fortress was abandoned. Darsin lay undisturbed for centuries. Circa 20 BBY, during the Clone Wars, the Chevin slaver Phylus Mon and the Human Dark Jedi Karae Nalvas traveled to Almas along with several of their minions and explored the Sith fortress. They came in search of the secrets of the creation of Sith battlelords, a class of warrior leader developed by Darth Rivan that were bonded to their troops via the Force. When the party accessed a secret chamber inside the fortress in which the rites involved in the making of Sith battlelords had been recorded, Darsin's spirit was re-awakened and he attacked them. However, Mon used the Darkstaff—a powerful Sith artifact that the Chevin had been lent by the criminal Len Markus—to ward off the ghost, and Darsin watched helplessly as Mon and Nalvas made a failed attempt to perform the Sith battlelord rituals. Due to the artifact's presence, Darsin was unable to prevent Mon from leaving the fortress with one of Rivan's Sith tomes, much to the spirit's dismay.
Meanwhile, the Jedi Order hired the Heroes of Cularin, a renowned team of freelance agents, to investigate the disappearance of some Jedi Knights who had been captured by Mon's entourage, and two hours after Mon's incursion, the operatives made their way to the lower levels of the Sith fortress. Darsin observed the agents as they moved through the fortress, and he planned to ambush them.
When the agents entered the fortress' crypt, Darsin pounced on them, attempting to strike them down with six lightsabers that he wielded simultaneously through the Force. However, the agents overcame the spirit and threatened to use the power Force Light to destroy him. Darsin begged for mercy and told them about Mon's doings in the fortress, and the agents agreed to spare the spirit.
A weak-willed individual, Darsin was happy to take unfair advantage of others, and he had no qualms against lying to people or being manipulative to achieve his aims. Following his death, Darsin became corrupted by the dark side of the Force to a greater extent than he had been when he was alive, and he became vengeful, attacking intruders who entered the Sith fortress. He disliked being tied to the fortress' dark side aura and he sought to be freed so that he could go where he pleased. When Darsin was re-awakened by Phylus Mon's violation of the Sith fortress, the spirit was enraged by the Chevin's actions, as he believed that Mon had no right to steal Darth Rivan's secrets and because Mon was carrying the Darkstaff, which had been feared by Rivan more than anything else. The spirit felt humiliated when Mon countered his attack, and he became angry at himself, because he could not pursue Mon's party beyond the bounds of the Sith fortress and kill them. Darsin feared the Heroes of Cularin when he encountered them shortly after Mon's intrusion, because he realized that they could potentially destroy him. As a spirit, Darsin manifested himself clad in flowing, black-colored robes.
Darsin was trained in the use of Sith sorcery, and he was able to use the Force to sense the world around him, to move objects, to affect the minds of others, to heal himself, to enhance his strength and to drain Force energy. In addition, he was proficient in the use of the powers battlemind, Force rage, Force stealth and Hatred. In his incorporeal, spirit form, Darsin could not be harmed by physical attacks, and he could teleport himself at will to different locations within the Sith fortress. Before his death, Darsin imbued the crystals of six lightsabers with his essence; after he became a ghost, he was able to temporarily extend his presence into the weapons and wield them in combat. Due to a combination of the experiments that were performed on him by Darth Rivan and the dark side presence that pervaded the Sith fortress, Darsin had a greater power and control over his environment than did normal Sith spirits, a strength further enhanced after he was exposed to the Darkstaff.
Darsin was created by Morrie Mullins for A Mon Alone, a 2004 role-playing adventure that formed part of the Living Force campaign. The character was later referenced in the article Sith Battlelords, a tie-in to A Mon Alone that was written by Mullins and published on Wizards.com. In 2007, he received a further mention in the roleplaying module Echoes of the Jedi.
In A Mon Alone, the player characters role-play as the Heroes of Cularin, and the decisions they take impact Darsin's actions and ultimate fate. If the player characters spend a long time in the fortress' library, Darsin attacks them there, rather than in the stronghold's crypt, while if they respond to a call made to them by a voice in the fortress' ritual chamber for the agents to promise themselves to the dark side, they can be possessed by Darsin. If the player characters use the power Force Light to dissipate the fortress' dark side taint, Darsin ceases to be bound to the fortress and flees. Alternately, it is possible for the players either to destroy Darsin or to let him remain in the fortress in peace. Echoes of the Jedi later established that in the canon outcome of the encounter, the player characters defeated Darsin, but the adventure did not provide any further clarification of the canon events of the altercation. The body of this article depicts the outcome where the player characters agree to spare Darsin.