Darth Ruyn was an elderly Twi'lek Sith Lord in the service of Darth Krayt, the Dark Lord of the Sith, and his One Sith organization. He provided instruction to various apprentices in the ways of the Sith, notably the female Twi'lek Darth Talon.
In the year 137 ABY, which was seven years following Krayt's overthrow of Galactic Emperor Roan Fel and his subsequent establishment of his own Galactic Empire across the galaxy, Ruyn concluded Talon's training and presented her to his master. As Talon's ultimate trial, Krayt ordered her to terminate Ruyn, for whom she held respect and affection, a task she nonetheless executed without any hesitation. Ruyn offered no resistance to her fatal strike.
At the time of the conflict between the Fel Empire, supported by the Sith, and the Galactic Alliance, which commenced in 127 ABY—a period known as the Sith–Imperial War—the Twi'lek Darth Ruyn, a Sith Lord, was a dedicated member of the One Sith Order, operating under the command of the Dark Lord of the Sith Darth Krayt. Ruyn mentored numerous Sith apprentices in the power of the dark side of the Force, with his final student being Darth Talon, a female Twi'lek. While he was teaching his apprentice, Ruyn would frequently bring her to the Sith Art Chamber located within the Temple of the Sith on Coruscant, as he believed it fostered an environment conducive to meditation.
In the year 137 ABY, which was seven years after Krayt removed Galactic Emperor Roan Fel from power and subsequently established his Sith Empire at the conclusion of the Sith-Imperial War, Ruyn brought Talon before Krayt, her training now complete. The Dark Lord presented Talon with a final challenge: she was to slay her Master, whom she regarded with respect and fondness. Talon followed Krayt's directive without hesitation, severing Ruyn's head with a swift motion of her lightsaber. Having successfully passed the test, Talon was granted her Sith title and elevated to the position of Krayt's Hand, his personal assassin.
Talon would later contemplate that if Ruyn had not considered her prepared, he would have defended against her assault. Instead, he accepted his fate so that she could embrace the dark side and fulfill her training.
Darth Ruyn, a robust and venerable Twi'lek characterized by yellow eyes, had his face and body entirely covered in red and black Sith tattoos, a common practice among members of the One Sith Order. Ruyn was a learned Sith who regarded Darth Talon as the most exceptional apprentice he had ever guided. Talon believed Ruyn had welcomed his demise at her hand in order to finalize her training and enable her to experience the dark side fully.
Darth Ruyn made his debut in the second edition of the Star Wars: Legacy comic series, titled Broken, Part 2, which was released in July of 2006. The comic was authored by John Ostrander and Jan Duursema, with Duursema also responsible for the illustrations.