Universe Name: Earth-3
Power Limit: Continent-level
Quick description:
This is an alternate version of Earth in which the planet spent the majority of it's time ruled by immensely powerful magical beings referred to as 'Gods' or 'Celestials'. These beings controlled humanity, treating them as little more than cattle or pets, building immense cities and thrones as they performed their internal affairs. Approximately 3000 years ago, a mysterious being known as The Darkness invaded the Earth. Humanity rallied behind it and overthrew the Gods in the First Divine War. Of course this was a shitty idea, as The Darkness proceeded to torture and murder the entire human race for shits and giggles. This instigated the Second Divine War about 500 years later, as a host of humans was found who had inherited some degree of the Gods' powers. These humans banded together with the Gods, recovering ancient technology and magic to face off against the Darkness. In the end The Darkness was defeated, at the cost of the majority of the Celestial Race, as the most powerful of the Gods (Ra) sealed The Darkness in an extradimensional prison. Now the Earth is in a state similar to our Earth, with the Gods mostly forgotten, with the exception that technology is significantly more advanced and there are 'Mutants' with divine powers inherited from the torn up remains of the fallen Gods.
Technology:
Most of the planet is like our Earth, but military tech is way advanced. Think of it as a comic book universe, where the military still uses tanks but somehow everyone else has giant robots and death-lasers.

Universe Name: The Hellworlds
Power Limit: Planet Level
Short Description:
A universe that seems to both mirror and mock our own. It consists of a wide variety of planets floating through an immense magical soup, obeying no fixed orbits or gravitational laws. Each of these planets has wildly different climates that seem to be determined by their current rulers, some covered in buildings and others completely barren. This universe is filled with purely magical beings known as Demons, who live off the emotional energy provided by humanity. The greatest treasures in this realm are human souls, which can be used as powerful sources of magical energy and catalysts for demonic magic. They don't live off suffering exclusively, however, and many demons are just as happy living off of lust, happiness, depression, sloth, nostalgia.... you name it, there's a demon for it. These Demons are ruled by the Demon Lords, the most powerful of Demons, who live off the tributes offered to them by their subodinates. These beings would have enslaved Earth-3 ages ago, were it not for the fact that they are unable to enter it.

There are many theories that suggest that the Gods possess the same nature as Demons, but both sides heavily deny this. The Darkness is also well known within the Hellworlds, as it ruled the Hellworlds before it arrived on Earth. It is unknown whether it originated in the Hellworlds however, or if it is as alien to the Demons as it is to Earth.
Technology:
There's a certain amount of 'magical science' which is the study of magic. However most Demons have a short attention span and little interest in gaining knowledge, lacking humanity's natural curiosity.

Universe Name: Aegis
Power Limit: Continent Level
Short Description:
Aegis is a massive city that serves as the bridge between Earth-3 and the Hellworlds. It's a Sealed Dimension, and it's impossible to enter through conventional dimension-travelling. The city contains two Gates. The South Gate (or the Gate of Life) leads to Earth-3, and is guarded by the God of Life Osiris. The North Gate (or the Gate of Death) leads to the Hellworlds, and is guarded by the God of Death Anubis. Both gates can be accessed from multiple locations in their respective dimensions. The guardians of the gates allow anyone to pass, besides those who wish to unleash The Darkness once more, and they psychically probe anyone who enters or leaves Aegis. This is because Aegis serves as the Seal that hold the Darkness in place, in addition to the grave of Ra. Most are unaware of this however, and due to it's interdimensional location it serves as an embassy for Demons and Humans. It also lies outside the jurisdiction of both Earth and Hellworld governments, which has brought in a steady crowd of misfits and criminals. Aegis is ruled by 'the Mayor', a former farm boy who discovered the city first. He is assisted in this by the Knights of Horus, who keep the order in the central areas, while the areas away from the center are ruled by a wide variety of powerful demons, shady corporations and gangs.
Technology:
Both magical knowledge and technology is quite high here. This place serves as the ideal location for evil masterminds to retire and has it's fair share of mad scientists creating scientific abominations, in addition to being a place of great magic which attracts those few demons interested in the study of magic, as well as human spellcasters.

Don't worry, these aren't the deities from Warhammer 40K. I've scrapped those by popular demand. Instead these are the rulers of the Chaos Realm, a universe formed from the emotions of all humans combined.

Name: Lucy
Represents: Fear, Nightmares, Hope
Domain: Dark Woods Circus
Personality: Cruel, playful and inquisitive, often interested in interfering with the affairs of morals. Highly competitive, and wishes to 'deal' with the other Chaos Gods so she can rule the Chaos Realm alone. Will happily offer rewards of power to those that do her bidding, seeing mortals as mere toys to be played with.
Appearance: Her favorite appearance is that of a small girl wearing a pink dress. However, she also often appears as an immense spiderlike monstrosity, covered in barbed tentacles and screaming human heads.

Name: Bob
Represents: Art, Creativity, Curiosity, Insanity, Contracts
Domain: The Great Theater
Personality: Incredibly random, Bob ranges from a friendly figure to a destructive force of nature. He draws great pleasure from surprising mortals, and seems to draw an odd pride from the accomplishments of intelligent races. He often interferes with mortal affairs, but does so in widely varying ways. His attitude towards the other Chaos Gods is equally incomprehensible. Seemingly contradictory towards his chaotic nature he enjoys forging contracts with mortals, often granting them their greatest wishes at a cost. The cost, however, is often far greater than it seems at first, although Bob is incapable of breaking a contract once he has made it and must abide by the terms.
Appearance: Bob's favourite appearance is that of an inhumanly tall figure clad in a brightly coloured tuxedo and a top hat of similar colours. His clothing constantly changes colour and is usually ridiculously shiny. He also carries a cane within which he's bound the souls of artists who forged a contract with him. While he often changes his appearance, he usually looks human.

Name: Jeffrey
Represents: War, Destruction, Honour, Pride, Courage, Death
Domain: The Eternal Battleground
Personality: Brutal and uncaring, Jeffrey is constantly consumed by a desire for combat. He revels in a challenge, and will often limit his powers in order to make a battle worthwhile. He faces his opponents with honour, and cares little for the morals or reasoning behind combat. He fights for the sake of fighting itself. He often attempts to battle his fellow Chaos Gods, not to conquer their Domains or to increase his own power, but simply because he enjoys the thrill of battle. While he relishes each victory, he draws the greatest joy from being defeated in honourable combat, and because of his carefree disposition he is almost always in a good mood. Jeffrey is less inclined than the other Chaos Gods to involve himself in mortal affairs.
Appearance: His favourite appearance is an immense collosus made of steel covered in spikes, blades, shields and weapons. His eyes are large pits of glowing metal, and globs of molten steel occasionally fall from his face as he moves. He always wields an equally immense weapon, although the weapon in question often changes. Every single blade and plate that makes up his immense body is inscribed with the name of a great warrior that once wielded that blade or plate of armour in battle. He can also take the form of an immense dragon with golden scales and claws and teeth forged from adamantium. When in battle, he often alters his appearance and size to reflect his opponent.

More Chaos Gods may be added in the future.