The Western Tails RPG takes place on what could be a parallel Earth, where a meteor struck Nevada in 1843 and released a type of mutagenic virus onto the world. This protean virus seemed to affect mostly the primates and lower lifeform bugs in the area. Mainly spreading through humans, the virus was not noticed as its effects were minuscule at first, just starting as sweats, fever, and tiredness before the infected would slip into a coma-like state. Once unconscious the virus continued its work of converting cells and rewriting its host DNA to closer match that of another within the area that was better adapted for the environment. This process was slow, taking months to fully convert its host. The virus kept the body alive in a hibernated state during the conversion process, once the conversion was completed the virus went dormant.

These new furs would wake from this Great Sleep in a location that was familiar to them but also, strange. Their world seeming off somehow, as if they had just woken from a dream. Their minds still remembering how to do basic things, like walk and speak but not remembering how they got to where they were, or who they really are. Over time they remembered more, like where they lived or how to do their jobs but still unable to recall what they were doing before, or why some of their clothing did not fit anymore. Scholars have tried to learn more about the time before, studying the books, images, and items about the lands in hope of learning what had happened, and who the strange ape-like creatures in many of the images are as well as what happened to them. Most of their research not concluding if the Ancient Ones are even real, or just stories. Over time many have forgotten about a time before and moved on, adapting to these new lands, converting the ancient one’s devices to fit their own needs, or creating new ones. while some still try to find answers to questions that might never be able to be figured out.

The Western Tails RPG is set in the years following the change, with most of the settings in the book being on the West Coast and primarily in Oregon. However; the setting can be any time and any location as traveling can happen. By the year 1850 many of the settlements that were damaged in the calamity that changed the world are built back up and adapted for many of the new forms the people have. Though, settlers moving west still have to deal with the vast barren plains, tumultuous rivers, dangerous dust storms, and deadly bandits. An influx of those coming north looking for gold has also brought many new furs to the area, which is making many of the natives uneasy as settlements expand, while hunting and sacred lands are claimed.