A shikigami is a spirit created by a magician to fulfill a specific purpose, but most magicians do not live forever. They end up set free after the completion of their purpose or the death of the magician. Most of them end up propositioned by gods or other spirits to serve under them or join their communities. Many end up in The Forest Of Love or become spiritual healers under Nui or The Maiden Made Of Light. Other less common fates are to become spirits of The Lady Of The Waves or The Jade Chairman. Regardless, the shikigami who do not end up associated with gods or deities usually go to the cities of the spirit world where they fulfill roles somewhat similar to what they were programmed for. Those who refuse or who want to be with other similar spirits go to Shikigamimura, where retired shikigami live free of needing to fulfill any specific purpose. It is not a large city, but it has many tall buildings with no roads, as if skyscrapers were randomly built in forests with minimal disturbance to the trees and wildlife. Most buildings in Shikigamimura are connected by elevated indoor bridges and the city has a large wall made of glass and metal. The buildings of Shikigamimura resemble octagons and other unique styles that Shikigami have created or created from their time in the spirit world. Unlike other cities, there is not a consistent building style as there are a lot of different kinds of spirits who do not feel the need to impose conformity on each other. Many buildings in Shikigamimura are floating or have illogical or impossible designs that can only exist in the spirit world.
You can gain the attention of any shikigami or gain them as companions, but they are all so unique and varied that there is no way to know how to get this to happen. Most do not harm anything but some may do baneful actions for various reasons.