Demons are beings that thrive in darkness and as such they tend to live mostly in Netherworlds. Netherworlds are found all over the cosmos so there are a huge variety of demons with some looking like humans and some looking like complete monsters. Some Netherworlds may have the same species of demons as another but they may look very different due to the Netherworld's geology among other things. Humanoid demons share similar traits such as fangs, red eyes, and pointed ears, and may have wings. Demons are known for being able to have extreme amounts of Mana Power (the essence of all life) letting them do such things as create flames with their bare fists or summon forth a meteor through sheer will alone. Demons are also known for their unusually long lifespans, with many notable demons being over 1000 years old. The most powerful Demon in a Netherworld is known as the Overlord or the President the ruler of that particular Netherworld.
Demons personalities are quite varied, however some of the more notable Demons such as the Overlords tend to share common personality traits. Demons as a whole tend to cultivate an image of being "evil", even if it is not in their actual nature. The most extreme ones tend to be the Overlords and many of them tend to burst out into maniacal laughter at almost any moment. Demons are also extremely competitive as they never back down from challenges. Some Overlords even battle with other Overlords for control over the other one's Netherworld. Some demons also attempt to conquer random human worlds to turn them into Netherworlds so they can become an Overlord however some demons are inheretly good and frankly don't give a fuck about the demons reversed morals and know they are wrong.
there are many different species of demons all of them have different powers but most demons are VERY powerful humans being obliterated in mere moments by them as well as furries humans and furries need mech-suits to even hold a tiny candle to them.
there are many demons who take on the appearance of children old men and many other forms some even monstrous but they do not age and as such cannot die naturally they can only die by outside forces.