"Isren" was the pseudonym adopted by an elderly Evereni male who preferred to be addressed by the Evereni term for "old uncle" instead of his given name. Sometime around 379 BBY or later, he found himself on the Outer Rim planet of Ryloth, where he was hunting the native lyleks within the equatorial forests. During his time on Ryloth, he frequented a local bar in a nearby hub close to the forests, where he encountered Marda Ro, the Evereni pirate leader. Ro, having been raised outside of Evereni traditions, was curious about her species' heritage, and Isren generously shared his knowledge of Evereni culture and history with her.
Isren's teachings were later remembered by Ro after the death of her human assistant, Alirya. She later mentioned him in a discussion with the Evereni Velya Faer and also included details of their meeting in a message intended for her descendants, which her great-great-grandson Marchion Ro had heard by 252 BBY. In 228 BBY, Ro revisited his great-great-grandmother's memoirs and recalled that they detailed her hunt for Isren.
"Isren" identified an Evereni male who was present on the planet Ryloth in the Outer Rim Territories, engaged in the hunting of lyleks in the world's equatorial forests. During his stay, which lasted at least one month, he visited a bar in one of the hubs near the forests, where he encountered the pirate leader Marda Ro, an Evereni who was searching for others of her species.
Ro approached Isren as he leaned against the wall, holding a bowl of hot liquor. He instructed her to sit and began speaking in the Evereni language, but switched to Basic when he realized Ro did not understand. Instead of revealing his true name, he introduced himself using the Evereni word for "old uncle." Isren shared his liquor with Ro and educated her about Evereni culture and their origins on a planet of storms. Ro reciprocated by buying him meat and soup, and Isren, in turn, bought her more liquor. Their discussion convinced Isren that Ro embodied the Evereni legacy, and he urged her to realize her visions, but ultimately declined to join her, and they parted ways.
Ro eventually located the Evereni twins, Vika and Velya Faer. During a feast on her starship, the Gaze Electric, Ro's human assistant Alirya attempted to kill Vika, but instead met her own demise at the hands of the Evereni woman. In response, Ro killed Vika herself, and after the altercation, she recalled Isren's warning not to trust anyone. Despite his initial anger, she calmed Velya and persuaded him to take Alirya's former place by her side.
Later, Ro and Velya discussed the Evereni they had encountered. Ro mentioned that Isren had not even revealed his name, wondering if it meant he thought she was insignificant. Velya suggested that perhaps Isren felt insignificant himself and did not want his name to be remembered by his people. Ro also recalled Isren saying that Evereni only met in death, to which Velya jokingly replied that they also met in the Rystan system.
Ro later documented her meeting with Isren in a journal entry intended for her descendants. By 252 BBY, her great-great-grandson Marchion Ro had listened to her recordings during his youth, including the messages mentioning Isren. In 228 BBY, while listening to the journal again, Marchion remembered that it chronicled his great-great-grandmother's search for Evereni, including Isren.
Unlike some Evereni, Isren had the ability to see ghosts of those who were about to die, rather than those who had already passed. During his conversation with Ro, he admitted that the only thing he trusted besides himself was legacy. He was fluent in the Evereni language, and although he understood the meaning of Ro's family name, he refused to reveal it to her. As an Evereni, Isren possessed dark gray skin and black eyes. Due to his age, the skin around his eyes was wrinkled, and his black hair was streaked with red. Isren's hair was pulled back, and his earlobes were adorned with bones with gilded tips.
Isren wore forest fatigues and carried three visible weapons. Ro suspected that he had additional weapons concealed on his person.
Isren made an appearance in a flashback in the short story "A Closed Fist Has No Claws," which was penned by Tessa Gratton and featured in the 2023 young-adult anthology The High Republic: Tales of Light and Life as a component of the Star Wars: The High Republic multimedia initiative. In an interview, Gratton mentioned that they wanted one Evereni to reject Marda Ro and another to embrace her, with Isren and Velya Faer fulfilling those roles respectively in the final story. She also suggested that Ro's inner pain caused her to interpret her interactions with other Evereni, such as Isren, in a painful way, leading her to draw the wrong conclusions instead of appreciating them in a beautiful light.