|Founded||5 Temporal 8784 GE|
Penumbra was a city founded by the Ráglauth's illithids. They built it over an entombed living primordial named Axinite. This ancient being has a massive store of psychic energy and came to be a source for psionic leeching - the draining of psychic energy from one being and using it to restore your own. Later, this primordial was opened up and crystal forges constructed inside its chest cavity. One of the greatest items to come from these Axinite Forges were the Silver Mirrors. These devices functioned like teleportation devices, allowing the illithids to leave Ráglauth for other moons and worlds.
Penumbra is also where the first Dromites were created. Similar to how psionic energy was drained from Axinite's body, which he welcomed, the illithids went a step further, stealing a part of his life energy to create a new race. In so doing, Axinite planted his own seed of retribution in the Dromites. He fortified their minds with a hive mentality, making them immune to certain psychic viruses and when working together, able to resist mental control.
When the illithids of Penumbra formed the Suellk empire, Penumbra became its capital. After taking control of Ghífthauk, the Suellk capital was moved to the captured githyanki city Incarsabec. This was done for military reasons, and heavily debated in the Psycharum. The military won out in the debates, and the capital was moved to the recently captured enemy capital.
In the Incarsabec Rebellion, Penumbra was depopulated by a virulent psychic virus. Unlike most other holdings that were caught up in this civil war, Penumbra remained untouched by military actions. Never breached in their history by enemy forces, the illithid city's defenses and remote location were not strong enough to keep out the psychic viruses. These viruses wiped out not only every sentient being in the city, but also swept the countryside of sentient life. As a result of these mind eating viruses, Penumbra, and possibly the entire moon became devoid of sentient life.