The Animal Kingdom was the first plane discovered by the Red Robes during their expedition through time and space.
The Animal Kingdom was a plane devoid of humans and entirely occupied by herbivore animals, even common carnivore species such as wolves are herbivores in this plane. The animals lived in settlements made up of numerous different species and had developed a common language for cross-species communication.
The Animal Kingdom had no written language and their history was preserved in oral tradition.
Originally predators hunted and ate other animals but over time they learned to live together and meat eating became a thing of the past. A loose governmental structure known as the High Court now rules over the Animal Kingdom. This court consisted of three massive beasts known as the royal beasts and they each represented an aspect of bestial nature: a Kodiak bear represented power, a snow owl represented wisdom and a one-eyed wolf represented instinct.
There is no record of humans ever existing in the Animal Kingdom and the Red Robes are initially greeted with fear, most animals simply fleeing from them. Eventually, Taako, Lup and Barry manage to befriend a mongoose family and they learn the animal language from them.
Eventually The Hunger arrived and consumed this plane's Light of Creation, ironically while the Royal Beasts were debating on if they should give it to the Red Robes or not. Due to this, the Animal Kingdom and it's entire plane were pulled into The Hunger and consumed.