The Void

In the world of Monument, a process of the afterlife is known. Human souls leave their body once they die, they then travel to the afterlife but along the way begin to shed away their regrets, emotions, ideals and other worldly thoughts and feelings to become a true, pure soul. It is not known where these souls go once they have been purified but their impurities fall down into a place known as The Void.
These impurities coalesce with similar impurities and form beings known as Void Kin. Void Kin are composed of hundreds of instances of emotions, regrets or thoughts that occupy people when they were alive causing them to express these thoughts or feelings fairly strongly. When an emotion that is considered an 'impurity' is so common throughout Humanity, it coalesces into an extremely powerful Void Kin called a Monument. 
Void Kin vary in personality appearance and powers though most only have a single power that they can exert. Some people have such powerful regrets or emotions unique to them coursing through them that a majority of their personality before they died is transferred to the Void Kin that they create. 
Void Kin, by and large wish to travel to the Material Plane so that they can fulfil the regrets, desires or wishes that they are composed of however there are very few methods in which a Void Kin can travel to the Material Plane. Sometimes, a tear from the Material Plane caused by some Occultist or incident can allow Void Kin into the Material Plane, but by far the most reliable method of travel is by Contract.