Description:

An image of Level 10.1, an example of what could happen to nearly every level of the Backrooms under one potential occurrence of Phenomenon 25.

To describe it simply, Phenomenon 25 refers to the potential of immediate, yet completely unpreventable and undetectable havoc that would reign across the entirety of the Backrooms, specifically due to quirks regarding the mechanics of Liminal Echo and Level Evolution. As all aspects of the Backrooms are known to take their influence from the Frontrooms and evolve alongside it, it has been hypothesised that sudden changes to it could have drastic effects on the levels of the Backrooms. This specific theory of sudden change relates to a world-ending event on Earth being mirrored in the Backrooms because of the two aforementioned effects, effectively killing most people in the Back and Frontrooms if it occurs.

Any number of apocalypse scenarios can lead to Phenomenon 25 becoming a reality, but the three that are postulated the most are asteroid impact, mutually assured destruction through nuclear warfare, or global disease outbreak, ranked from most to least devastating.

Potential Effects

Regardless of what causes the instant destruction, its effects would mostly be the same, only varying in severity. The immediate effect would be the destruction or rising decay of almost all levels centred around man-made architecture, such as Level 11 or Level 0 itself. In truly apocalyptic scenarios, even nature-oriented levels would scorch and potentially become uninhabitable. Levels not based on Earth's nature or man's architecture could suffer a less cruel fate, such as Level 202 or Level 404, but in the event that little to no humans survive what causes Phenomenon 25 back in the Frontrooms, they too would break down and cease to exist win the absence perception and cultural understanding.

While it is believed that an asteroid impact would scorch every single level into unrecognisable stone, sand, and glass for millions of years, mutually assured destruction would at least leave chunks of the Backrooms inhabitable and potentially recognisable.¹ It is believed that Liminal Echo and Level Evolution would cause all architecture-based levels to shift into decaying ruins, scorch a great number of rural levels, and hypothetically spread radiation across almost all of the Backrooms, but as the nuclear fallout would (hopefully) not be equally spread across the Earth, levels (or small chunks of levels) would come out less scathed than others.

What is true for all three is that without humans and a rapidly evolving world for the Backrooms to copy, many of its systems may break down. Weather may get worse and more anomalous, day/night cycles may cease or grow erratic, or celestial bodies may cease to exist outright. More 'Backrooms Weirdness' could develop from this breakdown of systems, causing either increased or decreased Non-Euclidean properties, the latter of which could cause levels to shatter and break when their 4th dimensional geometry tries and fails to normalise.

It is assumed most people within the Backrooms would perish if Phenomenon 25 ever comes to pass, especially ones in urban levels. For those that do survive, however, the next barrier to overcome would be food, water, and shelter. As the amount of pre-packaged goods declines on Earth, so too would the same supplies in the Backrooms. Growing food would become a necessity instead of an alternative to scavenging, and any locations with drinking water would become safe havens. It is unknown how many more lives the aftermath of Phenomenon 25 would claim, but a great many would die from the changed landscape rather than the transition to that landscape in the first place.

An abandoned railway track in Level 713, showcasing another potential effect of Phenomenon 25, more specifically what could occur years, decades, or centuries after it happens.

Assumedly, multiple years and many lifetimes after Phenomenon 25 happens, the Backrooms would begin to heal as the Earth does. This would most likely cause all levels to have an abandoned look to them, or to begin resembling primitive structures that surviving humans or a potential second sentient race constructs. Evidence of meteor impact or nuclear Armageddon would subside to generic ruins, and given enough time the ruins would disappear through Level Evolution much like how they would in the real world through general decay and age.

Given enough time, the Backrooms would heal, unless some unknown cosmic threat is able to destroy the universe in its entirety or shred the Earth into scraps. Assuming that does not happen, and that humans survive a world ending disaster, we would return to the usual surviving and living we always have. The only difference would be an influx of sudden new dangers and a total breakdown of the systems we have relied upon, which would be much the same for those living the apocalypse in the Frontrooms.

As a brief but related point, it is believed that slow apocalypses, such as a failure to effectively stop global warming or the eventual expansion of the sun, will not cause the same Sudden and Instant Destruction, but will have some form of effect on the Backrooms' ecosystems. Given enough times, entities would evolve alongside the gradual changes that come alongside the rest of the Backrooms, as well as the other items and phenomenon. In the case of these gradual declines in Frontrooms quality, the Backrooms would only shift alongside it, and not undergo its own apocalypse.

Frequency:

Unless the future of Earth is incredibly unlucky, Phenomenon 25 would realistically only happen once for a considerable amount of time. There would hypothetically be the potential for mass disease outbreak, followed by nuclear destruction, and by sheer coincidence a meteor impact on the planet, but the odds of that occurring are incredibly unlikely.

There is also the potential that this phenomenon never comes to pass, whether because the mechanics of Liminal Echo and Level Evolution do not work as theorised, that the end of society never comes, or because the end of society happens at a gradual rate. No hypothesis is any more true or false than the other, and by design the phenomenon's frequency remains in the realms of speculation.

Discovery:

Discovery of Phenomenon 25 could only be made if Phenomenon 25 were to occur, unless meteorologist reports or early warning systems find their way into the Backrooms before events happen. However, if they did, there would be nothing that could prevent it.