In a faraway plane, beyond the fabric of the main plane of reality, was the Infernal plane of existence. A plane that was created by the great primordial god of chaos himself. An incredibly ancient plane, its history dating back to the beginning of the main plane, that encompasses all that is chaotic and mind-warping in nature.

It stretched infinitely, ever-expanding. It is so vast that its almost omniscient creator gave up on calculating its immeasurable size. The plane is composed of fire, water, earth, wind, darkness, chaos, and void elements. While mutated flora, fauna, and fungi grew on its corrupted soils and water, most of them are not suitable for consumption, and the amount is far from enough to sustain the vast amount of life on it. Instead of a natural life cycle, with plants, herbivores, and carnivores, the life cycle on this Plane is based mainly on carnivores! They ate each other for sustenance, as well as for evolving into new heights!

How can such a life cycle sustain itself for so long? Simple. The plane itself gives life through its warped energies. It randomly gives birth to countless creatures of demonic, abyssal, and eldritch nature and power. Some were born as strong as demigods naturally, able to lift mountains and split the earth asunder, but most are born weak at the bottom of the food chain, destined to scrap for food and be eaten. When a creature died, its energies would be recycled, giving birth to new creatures.

But, how can such a plane continue to grow? From where comes the supply of new energy to sustain its ever-expanding growth? From where does the infinite supply of souls, the thing that is crucial for any living organism to live, is supplied from? The answer is the main plane, the multiverse, the unending sea of energy. The infernal plane, like many other planes, has a symbiotic relationship with the main plane. In exchange for receiving the power of faith, sinful souls, resources, and whatever else, it gives back things to those who supported it.

Be it specialized resources, power, bloodlines, bodily improvements, and even its children... It will give them all... For the right price. After all, the one that wins in each of those transactions is non-other than the infernal plane. When you gamble souls, the house will always win.

The ones who manage this vast and nigh-infinite plane are the demonic gods who rise through the ranks through constant slaughter. Among them, there are seven entities of vast and ungodly power, only beneath the creator of this plane. They are known as the seven deadly sins. Each one of them has bathed in the blood of countless entities, godly or not. Each one of them encompasses a certain aspect. 

Pride - He who feeds on the Pride of others. Pride, the feeling of excessive superiority over others, excessive love of self. The want for dominance, to be unparalleled, to hurt others in the name of making themselves feel superior. To want to be more beautiful, richer, stronger... At the expense of the innocent. It is the chief of narcissism, vanity, and vain-glory. It is an empty perfection, a beautiful shell... Of nothing. Demons of pride are masters of the empty and all-consuming black flame of the void, as it mirrors their sin.

Sloth - He who feeds on the Sloth of others. Sloth is sadness, lack of motivation, apathy... It is laziness. It is the unwillingness to act. While the act of laziness does not directly harm anyone, it does, in fact, harm those around you. Unlike their vice, demons of sloth are masters of wind magic and are known as the fastest creatures of the infernal plane... When they are motivated enough to move, that is.

Greed - He who feeds on the Greed of others. Greed is, simply put, the desire to hoard things, a vice. Be it currency, power, women... The desire to hoard these things excessively for yourself is greed. It is to backstab others for personal gain. It is to be blinded by your own desires for wealth. It is to steal and rob through any means, be it through violence, trickery, manipulation, authority, or any other means. The demons of greed specialize in earth magic and are the toughest demons, reflecting their earthbound sin for material gains.

Wrath - He who feeds on the Wrath of others. Wrath is uncontrolled hatred and anger. While it does encompass pure violence, it is more than that. It also encompasses all acts of revenge that include assault and murder. It is the wish to harm others. Among the seven sins, wrath can be described as the possibly least selfish one, as it can also encompass justice and vigilantism. Even if one is selfless, one can be wrathful. It is the love of justice, perverted into violence and revenge. Demons of wrath are physically stronger and have mastery over fire, reflecting their destructive sin.

Gluttony - He who feeds on the Gluttony of others. Gluttony is the sin of excess, over-indulgence, and overconsumption. It is to enjoy food in excess at the expense of others. It is to live for the sole purpose of eating the next day. Demons of gluttony possess the most abundant energy reserves among all the demons and possess mastery over water magic, reflecting their sin that could swallow the sea.

Envy - He who feeds on the Envy of others. Envy is the sin of coveting what belongs to others. It is the insatiable desire to have what belongs to others for yourself. Even if you have a better house and lawn than your neighbor, you would always think otherwise. It is to enjoy depriving others of what belongs to them. Demons of Envy are masters of dark magic and possess special eyes, reflecting their equally dark sin and covetous eyes.

Lust - He who feeds on the Lust of others. Lust is not simply an excess of carnal desire. It is an excess of love for others. Be it the love for yourself, friends, family, loved one, an animal, an object, a concept, your God... Anything. It is the chief concept of love being warped into something ugly and corrupted. Enjoying the act of rape, indulging in the act of slaughter, reveling in vain acts, relishing in food too much, coveting your neighbor's spouse, enjoying money too much, initiating wars of faith in the name of God, or even liking the act of doing nothing... It is the act of loving something to the point it harms yourself or others. Demons of Lust enjoy beauty only equal to demons of pride, a body that could limitedly transform, manipulate lust, and drain life energy, and are masters of mind magic. It is a reflection of their beautiful yet equally mind-warping sin.

Whenever someone sins in the main plane, it is like worshipping one of the seven sins. It is their food. It is their faith. However, the demons themselves are not necessarily evil, nor are they controlled by their sin. It simply creates urges inside them to lean towards their sin.

Forming a familiar contract with a demon is frowned upon in many cultures. It is because of their effect on the psyche of the summoner. The higher the grade of the contract, the more it would affect the summoners psyche. While it doesn't exactly turn someone into the incarnation of that sin, it does make them lean towards it.

For example, those who sign a contract with a demon of wrath become more violent. Greed makes them covet wealth more. Lust increases carnal desires...

If a clean man signs a contract with a demon, then, at most, he becomes more prone to sin on a healthy scale. However, if the person was already prone to sin in that aspect... He might be controlled by it.

A demon doesn't necessarily belong to one of the seven sins. However, belonging to one is tantamount to being demon nobility. The more highly evolved the demon, the nobler it is. Also, sin demons resemble humans, apart from their retractable horns, tail, and wings.

The weakest creature in the infernal plane is non-other than the grey demon. The grey demon is rank K and only the size of half a toe. While it is weak, it also has incredible potential. It can evolve into any demonic creature out there, including into a seven sins demon. While the chance is abysmal at best, those who manage to evolve are elites among the elites and possess far more powerful skills than naturally born counterparts. As proof, many of the past and present of the seven deadly sins were once grey demons.