Solara was the essence of Halla and a physical manifestation of the achievements of mankind. A planet covered in Dark Matter and teeming with the spirits of the territories, Solara was the birthplace of Saint Dane , the Travelers, and the Travelers' surrogate families. As Saint Dane took over Halla, the power of positive Solara slowly dimmed as the positive aspects of mankind faded away. When your physical form dies your spirit is sent here. You see only what is most appealing to you here.
Free will and balance fed positive Solara (Heaven). Fear, oppression, greed, and the like fed the negative Solara (Hell).
In the Horizon Compounds, non-Ravinians were at mercy of the crime, disease, and outright abuse bestowed upon by the Ravinians. Their only happiness was when they slept. Fear and agony was all that they fed Solara with. In the Utopias, there was pride without humility. Strength and power without restraint. Greed without generosity (on Quillan). Humility, restraint, and generosity were what fed positive Solara.