The Illia galaxy, also just called Illia, was a nearby galaxy to Gallifrey.
Like most galaxies, Illia contained stars, clusters, nebulae, planets, moons, and creatures. It was the location of the constellation of Sephin, where conflict between the Time Lords and the Nestenes broke out. Rassilon ordered for his forces to confine the enemy within the galaxy, where most of the worlds were enslaved and became protein planets or Auton factory worlds. He later used the Moment to destroy the galaxy and all life within, including the Nestenes and their slaves. (PROSE: Pandoric's Box)