Spirit energy is the energy present in the spirit realm or spirit plane.
Spirit energy is accumulated as one lives their life. The energy is gradually gathered with the passage of time. So if a being dies, and if it had a powerful spirit it’s soul goes forward but its spirit energy stays as a ghost or spirit with its memories. They are called spectral spirits.
Each spirit energy one gathers is connected to memory. If he is able to retain spirit energy then he is also able to retain memories that are attached to the spirit energy as well.
But unlike soul energy, some quantity of spirit energy always gets dissipated as the memory is forgotten. So people have come up with ways to store spirit energy either by use of mematites or spirit crystals or memory crystals.
One way to gather more spirit energy is by spreading consciousness and thereby gathering information around one thereby making memories and thus storing spirit energy. These spirit energies can be used with the lose of these memories. If a lot of spirit energy is used then memory loss can occur.
The spirit energy gradually dissolves back to the spirit world and thus ghosts and spirits fade away with time. This will happen unless they are bound by something that connected them with material plane. Usually, ritualists use the bones of the spectral spirits when they used to live to bind the spectral spirits to the material realm. The bones so made are called scrims.
Also sometimes when the spirits pass to the spirit realms, they sometimes retain the memories and when similar memories gather, the spirit energy fluxes greatly and this lead to a process of convergence where new beings are created in the material plane. Most of these beings formed do not breed but sometimes new races have formed because of convergence. These beings are called descended.