Sephi were a sentient species of humanoids, native to both Isobe and Thustra within the Thustra system. Notable traits included their extended lifespans and a natural aptitude for droids and other machines. A distinctive feature was their long, pointed ears that exhibited a range of movements, such as twitching, swiveling, and flattening, reflecting their emotional state. Their skin could be shades of peach or lavender, and their eyes were typically green or blue.
An ability developed by Sephi ancestors as a defense mechanism involved emitting a pheromone. This pheromone could induce unconsciousness in other beings, accompanied by a sensation akin to approaching death. The Sephi were known for constructing aerial vehicles called flyers.
During the High Republic Era, Tey Sirrek, once a Guardians of the Whills member, became a thief on the moon of Jedha after losing faith in the religious order. Eira Tay, a female Sephi, served as an engineer on the freighter named Eclipse.
The novel Tarkin, penned by James Luceno and released by Del Rey on November 4, 2014, included a reference to the Sephi within current Star Wars canon. The species then made an appearance in "Mercy Mission," a short story by Melissa Scott, which was part of The Rise of the Empire, a collection of novels from 2015. The Sephi were later visually represented in "Never Far Behind," a comic strip created by Jeremy Barlow, featured in the thirty-ninth issue of the Star Wars Rebels Magazine, a German publication. Barlow stated that the species' name was inspired by their cat, Persephone.
Within the Star Wars Legends continuity, the Sephi initially appeared in Jedi: Yoda, the concluding issue of the 2003 comic book series Star Wars: Jedi. This issue was written by Barlow, with illustrations by HOON, and published by Dark Horse Comics.