Illiara was a galaxy visible from the Mikhal Outpost in the Delta Quadrant, slightly above and to the right of the Hanara constellation of the Anschlasom people. Illiara was located along the route from the Som to the Mikhal. (VOY novel: The Eternal Tide)
Billions of years ago, Illiara was known to the Anschlasom. When a group of them passing through the Som stranded on the Mikhal Outpost 10,000 years ago, they carved their astronomical knowledge into stone and a cave.
In August 2381, Federation Fleet Commander Afsarah Eden, Counselor Hugh Cambridge and the Doctor traveled to the Mikhal Outpost to investigate Eden's origin, which was linked to the Anschlasom. Looking on the artifacts, Eden remembered the names of Anschlasom constellations and galaxies. (VOY novel: The Eternal Tide)