Irei was a Force-sensitive female Nikto of the Kadas'sa'Nikto subspecies. During the Imperial Era, Irei was forced to hide her connection to the Force; although it was not strong enough to be trained, it was sufficient to put her at risk from the Galactic Empire. Keeping her sensitivity concealed, she apprenticed in town at her parents' droid repair shop. Eventually, she met Chellwinark Frethylrin, who was a female Keshiri training as an Imperial analyst, and they fell in love. Irei eventually confessed to Frethylrin—whom she called "Chell"—that she was Force-sensitive.
Irei's fears of what the Empire could do to her and her beliefs that the actions of each individual mattered made Frethylrin question her loyalties. In part because Irei's parents also worked for the local Imperial garrison, putting them in frequent constant contact with Imperial officers and stormtroopers, Irei was often under surveillance. Frethylrin began manipulating routine surveillance data in an attempt to hide Irei as well as altering records and reports containing Irei's name. Meanwhile, Irei hoped the couple could flee and go into hiding, and she began to envision and design a device called the Shroud that would theoretically help them do so. She worked on it for a year and pleaded with Frethylrin to desert, but Frethylrin refused due to her fears and naive belief that she could change the Empire from the inside.
Frethylrin's work backfired and drew attention to Irei. The Empire burned down the repair shop, leaving Frethylrin to believe Irei had been captured or killed; in actuality, the Nikto girl had escaped.
As with other Kadas'sa'Nitko, Irei's skin was green and scaled. She also had clawed feet and hands; when nervous, she would chew one of the latter to the quick. With a height greater than that of Cal Kestis, who was 1.82 meters tall, her embrace let the human man enjoy feeling like he was small and fragile in comparison.