So I came up with this as how the world develops from a cambiran-coniferous era to an iceage-eocene era for the collaboration piece and I'd like to see how people play with the world.

If anyone needs help or wants ideas, I have several resources on cultures, ancient techniques and technology, and ancient animals.

First world: The first world is very primitive. mostly invertebrates in the sea, lots of shelled animals on shore, trilobites, and primitive vertebrates (no bones yet). Land is pretty much devoid of animals, save for bugs ranges in size from several feet to small. A thick layer of magic in the atmosphere covers the sky, making it permanently twilight, which means it ranges from orange to dark purple. Within this world is magic and magic races: elves, dwarves, pixies (name pending), and later undead humans.

Dwarves: Dwarves are stout and short, as usual, but like insects, they can see a larger spectrum of light than humanly possible. They tend to be 'in tune' with nature, noticing slight fluctuations in soil and water and are very knowledgeable about plants, fungi, and animals. They have bushy hair that resembles fire opals, in that they are dark with bright streaks of colors.

Elves: Elves are tall and skinny and prefer to live in natural caves, eating slimes, fungi, algae, and small water creatures. Elves have flat noses, but a strong sense of smell. They are mostly blind despite large eyes, seeing movement and intense heat. Instead, their long pale hair resembles moth antennae, sensing air currents and also great at detecting smells. Elves are far better at technological tinkering, climbing, mining, and spelunking than dwarves.

Pixies: Pixies are brainless things that may or may not be humanoid [insert cool idea here]. They're small, ravenous beings that live in low hollow hills. They don't stray too far from their hills, but they'll devour whatever comes near when they're hungry. Elves and dwarves don't know what they do, besides kill things, but the pixies regurgitate part of what they consumed. The pressure and processing by the pixies creates magic, stored in the hills like honey without honeycomb. Once a year, it erupts from the hills, covering the land in what is called The Heat, a dangerous wave of magic that is deadly to the touch, but seeps into the ground within hours and nourishes the land.

Humans: Humans don't show up until the pixies decide they don't want they're magic leaving their hills. The pressure and weight to the compact magic implodes like a star, both collapsing and exuding light, all the way up to and past the magic in the atmosphere. The light and magic striking the layer of magic resembles a sun--the first ever seen in the world.

The land becomes barren, driving the dwarves to burrow underground (save for criminals they leave to fend for themselves on the surface) and elves use their tinkering to live above the land and seek out resources, including shade from the sun.

Humans were a product of the implosion, most of them mindless and all of them dead bodies, killed by the pixies and put back together with magic. The magic preserves them and most are mindless, but a few are called Record Keepers and wander the world, exploring and learning about it to report back to the pixies, explaining the new world that has become a mix of hidden feudal kingdom and steampunk/clockpunk cultures.

The humans could hear and see, but beyond that, sensation was lost to them and they had a severe phobia of the dark, preferring to always remain in the light.

Second World: The magic implosion of the first world ceased, but not without consequences. It strengthened the magic in the atmosphere, making it denser and the change in gravity drew in an object in space slightly off course. The object slammed into the atmospheric barrier, the rock and the magic fusing under the pressure. The atmospheric barrier was destroyed, the object smashing apart and pieces falling to the planet. Flaming rocks struck the ground and sea, some burnt into the atmosphere. With the barrier gone, the stars could be seen, as well as a moon with a faint ring, what was left of the collision.

People had become a mix of the races from the first world as they lived through the cataclysmic change, becoming one single group, though aspects from their ancestors are common (short or skinny, colors in hair, blind, but can sense movement and smell well, sensation-less, etc).

The land had changed as well. There was an intense hot season, a cool season, and a cold ice age like season.

Still based on the four occupations of Japan, the land has been 'united', save for tiny towns or settlements deems insignificant. The place is ruled by unseen female magic-users and controlled by male magic-users who train raise an army of women. Families are allowed one female to carry on the family name and inherit property. Men are to work the land or business or to become wandering entertainers or academics. The army aids families in times of need, including if children are too scarce (the army of women is allowed to have children..

The cities are ruled by the army and magical children or women are taken to be trained. Magic is not genetic, but comes from bearing enough magic within one's body. People try to imbue themselves with magic via tattoos from plants grown in heavily magic soil or animals from water, or incense or food raised from similar places.

More in another post on the cultures (much shorter). I hope this isn't too confining, as you've got various hierarchies, tech, animals, landscapes, disasters, and races to play with.