Demons
Demons are the denizens of hell, and all have different purposes. Some are tasked with ensuring that the souls don't escape their eternal damnation, others are tasked with the punishment of the souls, while others are tasked with going to the human surface realm to tempt more people in committing sins or selling their souls so that they will end up in hell.
The Tenth Circle Academy helps to train the latter, ready to send them into the great wide world and bring as many souls to hell as they can.
Most demons were not born. There are two ways that demons commonly come into existence. The first is when someone dies whilst feeling strong negative emotions. As the soul leaves the body it fractures, with the fractured parts each gaining sentience and becoming a demon. These demons tend to be more prone to the emotions that brought them into existence, but they have no memory of the human's life.
The other method is through demonic initiation. Sometimes a human can be desperate enough to sell their soul, and a demon can make a choice. Either they do nothing and send their soul straight to hell, or they initiate the soul. Nothing will happen whilst the human is alive, but upon their death, they will have their soul dragged to hell. The initiated souls will feast on the energies of hell and grow more and more powerful. After a few years, the soul will be strong enough and that soul will be transformed into a demon with memories of their human life. These demons tend to be more humanlike in their behaviours, still being affected by their earthly wants and desires.
Powers:
All demons will have powers, but they likely won't be able to master those powers without training. Students can choose to have mastered 1 power, while teachers/staff of the academy can choose to have mastered 3 powers.
All demons will have powers, but they likely won't be able to master those powers without training. Students can choose to have mastered 1 power, while teachers/staff of the academy can choose to have mastered 3 powers.