Ysgard

The Heroic Domains of Ysgard is a Chaotic Neutral (Good) plane in the D&D Great Wheel Cosmology.

Diametrically opposite of Acheron; the two planes have many things in common: they are both planes of conflict and strife, the landscape is in constant motion and turmoil, and rather than playing home to one specific archetypical inhabitant, the planes are filled with a variety of races and belief systems who have cause to come into conflict with each other.

However, in Ysgard life is better because there are rich rewards and satisfaction for what an individual can accomplish, unlike Acheron where one successful conflict just leads into another one. The enemies in Ysgard often have legitimate grounds for fighting one another, rather than a contrived or forgotten reasons. Also in Ysgard, nothing is permanent, not even death. So while conflict and violence are commonplace, therefore nothing is outright malicious.

Just remember that despite being on the upper side of the wheel, it is not a plane of good. The plane does not exist for those who desire to enhance their personal growth or to contribute anything to those around them; those souls would be more likely to go to the neighbouring plane of Arborea. Ysgard is for those who can never be content with their lot and just want to pit themselves against something new and challenging, and thankfully the plane can provide that.

The plane is where dead heroes go, it is essentially Valhalla, the Viking plane of the afterlife. Many who come here get to drink all night and fight all day. At the end of the day, the plane's magic resurrects those slain in the day's fighting, and they all go in to get drunk and tell stories.

Layers

Again, much like it's opposite of Acheron, the landscape is an infinite void filled with floating matter that constantly moves around. The main difference is that land mass in Ysgard has no definable shape or permanency. The earth flows like a river across the void, constantly changing direction and topography. The only permanent features tend to be "inland" where the earth is less likely to take a radical change of direction and destroy what has been built.

Some land masses float entirely separated from the others, forming "earthbergs" that look like floating islands. These islands or even the the edges of continents can flow into each other, causing new mountain ranges to form. Or they pull apart, leaving empty space in the ground which can lead to the layer underneath.

Ysgard

The first layer is actually called "Ysgard", and it is the most populous of the three layers.

Ysgard itself has an appearance easily identifiable with the material plane, though with a lot more vibrancy and energy. The weather tends to be a lot more spectacular and the landscape is far more rugged and inhospitable. With the constant motion of the ground there are few permanent settlements, with the inhabitants of the land living in mobile camps or frontier towns with the occasional grand hall built at places of interest. Only the deities really have the power to mix the terrain into anything truly permanent.

Though with that being said, there is the great city of Himinborg, which houses the largest population in the layer (and likely the plane), which is based in the Plains of Ida, a large open expanse which holds daily festivals and markets.

The layer is also littered with battlefields, where armies have come together to fight one another for whatever reason.

A large region of the layer is called Aflheim (Elf-Home) where funnily enough, there lives a significant presence of elven petitioners and mortals. Aflheim has its own weather system and has a recognisable pattern of seasons, where in winter it gets so cold and bitter that the Elves have to retreat into caves to keep themselves warm.

Muspelheim

The second layer, literally underneath the first layer, is a realm of fire and hostility. The land has the fire-dominant trait and is replete with volcanoes and lava streams, and like the first layer the ground is in constant motion. If you're not fire-retardant you're going to be in trouble.

Fire Giants and their deities make their homes here.