The Memitim is the entity of Limbo, who resides within the gateways to both where souls go as well as the multiverse. They are responsible for the creation of the Psychopomps.
The Libra is a withering, unknown entity that oversees the balance of the Zones. With every action there is reaction. With every choice, there is consequence. It is the Libra who oversees this.
The Abaddon is the entity of the Dead Zone and Scheol, and is ultimately responsible for the amelioration of Revenants and Visitants, making sure that debts are paid for the price of bringing a dead thing back to the corporeal zone. This entity thrives off of destruction and conflict.
The Aegror is an entity that might have been behind the Dead Cell plagues that nearly wiped out the human population, as well as the cause of the time reset to zero (figuratively, not literally). It is an insidious entity that infects dead souls and, on rare occasions, the living. This entity is also capable of feeding off the other entities, as well as Psychopomps. Its only ally is the Wight.
Entities do not have faces or shapes, only genderless voices that speak within the Zones they assume control over.