The Wilderness of the Beastlands, or just the Beastlands, is the Neutral Good (Chaotic) Outer Plane of the Great Wheel cosmology of Dungeons & Dragons' Planescape setting. It is a plane of endless nature: vast forests of all kinds of trees, plains that continue on and on, huge mountain ranges, oceans dotted with countless island and great humid swamps. But that's not what the plane is known for or named after: it is all suited perfectly for every kind of natural creature imaginable: from tiny mice to collossal anthropods, from herds of grazers to singular predators: if it is an animal on the Material Planes, it can be found in the Beastlands. Anything from fish to mammals to birds to motherfucking T. Rexes and the more exotic things as well all make their home on this plane, living their lives of eating, migrating, reproducing and being eaten without sapient life intervening. It is a world of hunters and prey, surviving amongst nature and being part of it, rather than against it. It is a place meant for the fight of the fittest, nature at its purest. Because of how fitting the plane is to their wants and needs, the inhabitants often stay away from the portals to the other planes and layers.
The Beastlands have a strange effect on visitors: as they stay there their bodies exhibit a minor change to reflect their personalities. Strong people will grow tiger fangs or the fur of a bear, agile ones get monkey-like limbs, charismatic ones start to grow cat ears and so on. How fast this happens depends on your views: Lawful people can last days before the change sets in while Chaotic people start to change after a few hours. The change is not permanent: it remains in place as long as a person stays in the Beastlands and a length of time equal to their stay as they leave the plane.
Layers of the Beastlands
The Beastlands consist of three layers: Krigala, Brux and Karasuthra. Each of these layers is perpetually in the same time of day: afternoon, twilight or night. There are many between the three layers, though they almost always go to or from Brux. Those who do not often go to the Beastlands' neighbouring planes, Elysium and Arborea. And while the Beastlands are relatively safe in comparison to the other planes, it is not a very well explored place and still holds many wonders to discover.
Krigala is a layer of eternal afternoon, a warm sun basking the land in its glow. The temperatures on the plane are perfect for its diurnal inhabitants: grazing and hunting, migrating and reproducing. Two gods make themselves at home on this layer: Skerrit and Ehlonna. Skerrit is a lesser deity and the god of the centaurs: a benevolent and wise individual who is held in great esteem by his people. His realm looks just like the forests surrounding it, but it has a number of simple huts strewn around where the centaurs live.
Ehlonna in turn makes her home in The Grove of the Unicorns, a great cathedral of interwoven sequoias grown into a building. The trees are hundreds of feet tall, allowing birds to fly unimpeded. At its center lives Ehlonna, practicing her song and dance routines alongside the animals of the forest like she's a Disney princess. Spells cast within the Grove are Extended, and food/water creating spells are Maximized. And as its name suggests the Grove attracts plenty of unicorns, many of whom are Celestial unicorns.
Brux is a plane stuck in eternal dawn and dusk, colder than Krigala and often covered in fog and mist. The animals here are those who are active on the Material plane during the hours of twilight and would seek shelter during the day. If you ever get lost on this plane, find a river and go upstream, you will eventually end up on Krigala again.
Karasuthra is the most dangerous of the three planes. Covered in eternal midnight, only the moon with its slowly changing phases provides a bit of light that manages to pierce through the thick canopy of leaves. Many dangerous predators stalk the darkness, in search of prey and unwary travelers to devour. While the creatures here are very dangerous they are still Celestials, and will hunt evil creatures down without remorse. It is said that this layer has a close link to the Plane of Shadow, and that there are plenty of places on the plane where the barrier is thin enough to travel from and to the Plane of Shadow with ease. This would explain the large number of shadow creatures found on the layer, but this is not conclusive.
Almost all of the inhabitants of the Beastlands are animals in some way or shape. Petitioners who awaken here are turned into animals and live as such: while they can speak Celestial and can cast spells if they could do so during life they are still animals at heart and will attack any who threaten them. Hunters sometimes visit the plane in seek of great prey, but hunting here is difficult because of the intelligence of its inhabitants and with a bit of bad luck you are beset by a trio of Ankylosaurus who start breathing fire at you. Other visitors sometimes seek the wisdom of spirit animals who live there. All animals on the plane have their own lord: an animal that can turn into a humanoid shape. These are the Animal Lords: quasi-deities who protect their people from outside threats. The most famous one of these is the Cat Lord, who protects all large and small cats in the Beastlands. She has great animosity for Bast, the Egyptian goddess of pleasure and cats who might have something to do with the disappearance of the previous Cat Lord, who was quite clearly a different person (and claimed to be an ancestor of Gord the Rogue, however unlikely this is).
Some petitioners awaken in their old forms and gather in communities at the bases of great trees, where they stay as they turn into animals over the course of centuries, going from catgirls to furries to full-on animals. Other inhabitants include Skerrit's centaurs and the bariaurs in service of Ehlonna. Finally there are a small amount of the occasional inhabitants from other planes like archmages, but because of the nature of the plane these often seek other places to make their bases of operations.