Illyria was an inhabited planet located in the Vaultera Nebula. It hosted a Federation colony populated by Illyrians.
In the early 23rd century, Illyria accepted provisional membership in the Federation, under the proviso that they refrain from engaging in genetic engineering as dictated by Federation law. However, some Illyrian families continued to bio-engineer their children in secret, in accordance with their traditions.
After one such child, Ivan Ketoul, was exposed as genetically modified and arrested along with his parents, the persecution of Illyrians in the colony escalated. Illyrians were subjected to verbal harassment, denial of services, and even attacks; some moved to non-Federation worlds. The worsening civil unrest eventually prompted the local government to segregate the population into Illyrian and non-Illyrian cities. There were Illyrians who chose residence in the non-Illyrian settlement, though they lived in constant fear of discovery.
Una Chin-Riley and her childhood best friend Neera Ketoul were born on Illyria. (SNW: "Ad Astra per Aspera")
The name of this planet was only given in Chin-Riley's personnel file in "Ad Astra per Aspera".
The name was originally introduced by way of the episode title "Ghosts of Illyria".
In Chin-Riley's personnel file, she was said to have been born on Illyria or on Colony 9-A. However, a notation to her file stated that verification of her being born on this colony was pending and that the information came from an unreliable source.