Alicornutopia

Dreamshard is an Earth with a divergent history due to added magic elements. The degree of divergence is very similar to Alethia. The main cause of divergence is the existence of pocket dimensions around the worlds.

The Dreamshard and Dreamshapers
The Dreamshard looks like an ordinary gray quartz crystal. When it comes into contact with a sleeping or similarly unconscious individual that can sleep and dream it will turn that person into a dreamshaper, who will then start expanding their own pocket dimension.

Dreamshapers start without any control over their magic. At first they experience walking through their pocket dimension with about the same level of awareness of someone dreaming. They can eventually become lucid, but can’t wake up even if their true body is damaged. The only way for their true body to wake up is by having the dream-self pass through a portal and leave their dimension. This will cause the dreamshaper to wake and from that moment forth they will be able to use and control their dreamshaping once they fall asleep.

The traits of a pocket dimension are personality-based. A pocket dimension is a representation of a person’s mind taken form as a solid metaphor. This is not always straightforward or predictable. In a lot of ways, they work like enchanter’s mindscapes (from Effulgence’s Rêverie), but they tend to be more… landscapey and there is something that I would like to call a “narrative”. Felix’s dimension is a party, it has guests and it is welcoming and safe, which reflects Felix’s being/wishing those things. Fenris’ dimension is a corrupted version of his culture’s afterlife; it reflects Fenris’ vision of the world as imperfect, but with potential.

Dreamshapers can make their dimension grow in ways that fit their traits and “narrative”, influencing the dimension’s shape and placing portals where they want. Without guidance the magic just fills in the details, but depending on the specifics, a dreamshaper could make specific objects, building, creatures (or people) appear inside their dimension. They are limited to a growth rate of 3-4 km³ per hour of sleep.

Pocket dimensions
Pocket dimensions (as they are known in the USA) are also known as hiddenlands, otherlands or "little worlds" (elsewhere). They are extra-dimensional spaces that are separate but coexist with regular space. The vast majority of pocket dimensions are perfect spheres with somewhere between 10km and 40km radius and have 2 to 12 portals.
* Portals: They allow passage between pocket dimensions and Earth (or between two pocket dimensions) and look like a shimmer in the air that shows the other side of the portal through a transparent haze and can have arbitrary planar shapes. Keys (Capital 'K') is the term given to the circumstances which activate portals; there is a Key to open, close, lock and unlock a portal and they can be a wide variety of actions or conditions that have to happen near the portal or at least influence the portal's vicinity. Portals never intersect with other portals.
* Edges: Most pocket dimensions look like they go on forever - there are horizons with apparent geographic features, stars in the sky, etc - but if someone walks towards the dimension’s edge, they will suddenly experience a gray mist/haze over everything and if you keep walking the ground will suddenly not be there and you will vanish. People who vanish experience less than a minute of floating around and then landing somewhere else, but from the outside they are completely gone for several minutes and appear elsewhere near the dimension’s edge, nearer a portal, on another dimension, or even on Earth. This happens because they pretty much slipped between the “edges” of reality.
* Coterminous: Pocket dimensions coexist with a specific section of regular space, in a way that I can only describe as “they share the 3-dimensions but are one step away in the fourth.” The most practical implication of this is that if you walk into a dimension through a portal and then exit through a portal or vanish, you will find yourself having moved about the same distance and direction (some dimensions have weird spatial effects, but they aren’t the default.). There is some limited magic that allows seeing into pocket dimensions and this effect would be observed as the pocket being “layered” over the regular world.

So I asked Curious a buncha questions and I'm paraphrasing them here:

Where does the dreamshard come from?
It comes from another world (there are further worldbuilding details that may or may not be canon about this but this part is). It's been around for about a thousand years, brought by extradimensional visitors. These visitors had two other kinds of magic, and depending on the kind they have are called witch queens or skymages. The dreamshard's been in the witch queens' possession for a while but recently a fragment has escaped (it wants to be used).

What are witch queens?
They're people with magic that's sort of D&D-wizard styled, there are about a couple thousand of them in the world and they keep the means of learning their magic a closely guarded secret. There's a "Glam" factor in that they're more powerful when people know more about their powers/believe in them, and also when they fight a lot.

What are skymages?
Skymagery is hereditary and skymages have wings and weather/climate control powers. There are about a couple million of those in the world.

What do people know?
Witch queens, skymages, and pocket dimensions are all known. The origin of pocket dimensions is not known (that is, dreamshapers and the dreamshard are mostly secret, there are a few dozen of them in the world) except to a handful of people and witch queens. The witch queens try to keep the dreamshard secret, too, and not use it, but the fragment that escaped found its way to someone who used it to create lots of dreamshapers and Profit.

deep thread link to "something borrowed, something blue
"No, but dreamshapers, witch-queens and skymages are the most powerful by far and deserved to be talked about separately. From there there are various miscellaneous things like people that never get tired, people that can weave light into glowing cloth, talking fish that are people. There are various magical creatures like unicorns which have purifying properties, bats that can sense portals, shapeshifting animals... there used to be phoenixes but they went extinct because their eggs can make people immortal for five hundred years, one of the translation effects that I know off is granted by a two-headed snake that needs to lick your ears... there are magical artifacts that make you tired in exchange of granting telekinesis or telepathy, there is a type of glass that lets you see through dimensions. I think the other translation effect is an ambient effect attached to a specific dimension, some dimensions are always night but plants still grow normally there... the full list is going to be long."

The people that weave light into glowing cloth are called "Lightweavers".

Felix would find it endearing if his heart hadn't been ripped out of his chest recently. Felix offers more magical examples, they all keep interesting things but not as strong as the top three: Sea serpents! Flying animals of various types! A pocket dimension that gives telekinetic "phantom limbs" to people that lose limbs there! Berries that boost your singing ability, mute people that can eat said berries and sing divinely and control birds! scientifically inaccurate "prehistoric" animals that can be revived from their bones in this pocket dimension near Italy (this is a sentence in Italian)! Flying islands! Moving statues! Half-plant people! This place amplifies emotions! People that can animate wooden toys that protect children...

He eventually has to give a side explanation as to why so much of that magic was lost and why so many of the surviving magic people have recessive genes. Here are the wonders of thaumatophobic persecution! And why most of various magical people choose to live in either in the Stormlands and the Witchlands.

putting this here for reference.

More references
Dream of Electric Sheep

"Okay, we don't have anything that is as... high-tech as them. We have some animated statues like the lyhdynkantaja from this Finnish pocket dimension. They are made of bronze and have a lantern in their chests..." And Felix describes the lyhdynkantaja (which means lanternbearer) which can make binding promises that decrease their physical power if broken and increase it if kept. This can lead to respectively to death or "reproduction". The later by having the flame inside their body split and create a new lyhdynkantaja.

I failed to write down where their pocket dimension is, but it's somewhere on Finland.

"Physical power" basically means "mechanical power", a strong Lanternbearer is fast because they can apply greater force to their movements.

https://www.glowfic.com/replies/527750#reply-527750

Arthur smiles at Dayo then asks, "What does the one in Edinburgh do?"

"It's night all the time. People in there can sort of 'reach' for a star and take it, and it becomes a glowing glass bead that can be melted into glowing glass."