The mulefa world was one of numerous parallel universes in the multiverse.
Many of animals in the mulefa world evolved in a radically different way to those of Lyra's or Will's world. These animals did not have spines, instead having a skeleton based on a diamond-shaped frame with a leg at each corner. However, there were also vertebrates in this world, such as snakes.
The fauna known to inhabit this world were:
There was a large prairie in the mulefa world composed largely of knee-high grasses. There were also small bushes like juniper and flowers similar to the poppies, buttercups, and cornflowers in Will's world.
The most important plants in the mulefa world were the wheel-trees. There was a symbiotic relationship between the mulefa and the wheel-trees. The mulefa used the seed-pods as wheels, which over time wore them down so they could open and the seeds could be planted. The wheel-tree oil gave the mulefa consciousness.
The terrain of the mulefa world was covered in so-called basalt highways. The mineral composition of these lava-flows allowed them to flow for long distances across the savannah, and also made them resistant to weathering.