[PTTG]

4: Atmospheric ionization strips off 60% of Earth's atmosphere, resulting in chaotic storms before finally stabilizing just below a safe level for long-term survival at sea level.

The results of this are harder to approximate because it's not quite fatal. The supernatural ionization effects were bad enough, and resulted in an apocalyptic loss of biodiversity over much of the planet. The high wind speeds of the actual storm itself were severe, killing a significant but small portion of the population directly. In the days after, everyone above a few thousand feet died of asphyxia, ultimately killing around 10% of the population directly. Social collapse around the coasts due to storm destruction combined with migrant pressure killed more. Over the weeks that followed, it became clear that even at sea level, the atmosphere was dangerously thin. Combined with ocean outgassing releasing large quantities of CO2, the air gradually became more toxic to human life. Within a few years, the only safe way to do significant work on the surface is while wearing a modified SCUBA or other oxygen system.

By 2020, pressurized enclaves house what is left of technological society. Don't let the technology imply anything fancy, however; for the most part these enclaves are made by lining an existing building with plastic and then installing a compressor. The other remaining humans live on the coast itself in a permanent low-oxygen haze. The total population is now only in the hundreds of millions, split roughly evenly between the dizzy scavengers and the closed enclave members.

5: Solar disruption resulting in a more-or-less constant flare state. Less intense than #1, but still more intense than anything previously recorded and continuing for the foreseeable future.

This catastrophe is fairly cozy. Civilian technology and all long-distance communication is disabled, but hardened military computers and industrial tech still works. It's a hell world only in the sense that it's a collection of military dictatorships and standards of living have declined precipitously.

6: Magnetic field inversion. As the wave passes, like charges attract and dissimilar charges repel. Scientists would be able to perform interesting experiments in the picoseconds before every atom on the planet disintegrates.

No survivors. Teleporting to this worldline drops you in the middle of a new nebula created by the sun imploding and undergoing an exotic new type of stellar explosion.

7: Antimatter enrichment. The wave passes with minor magnetic disruption, but leaves a thick sleet of stable antimatter clusters throughout the solar system.

The antimatter clusters take the form of dust particles swirling in solar orbit. For ten years, each night was a spectacular aurora as the Earth swept its orbital path clear of antimatter debris. An orbital spacecraft receives slightly more gamma radiation due to the interactions with its hull, but in general the antimatter isn't hazardous. Within a few years magnetic capture technology allowed unmanned probes to scoop antimatter out of interplanetary space for merely astronomical costs, kick-starting space industrialization.

By 2020, the antimatter sleet has slackened somewhat, meaning the auroras aren't so bright, but there's still plenty of antimatter dust to harvest.

8: The asteroid belt is disrupted, causing a new era of asteroid impacts throughout the solar system.

For the traditional Lucifer parallel.

9: Ozmic enrichment causes space, but not the surface of any planets, to become a very-high-mana environment.

Like #7, this causes rapid space advancement, but it takes a little bit for it to become clear what's going on, and once it does, science starts to lose its mind. It's impossible
for magical effects to occur on planets (for reasons,) but once someone in space started working with magic seriously, it didn't take long to, for instance, produce a mundane
spacecraft capable of landing on Earth and recover people using magic. It's also quite easy to fly vertically into the mana feild and then use magic to provide the majority of orbital velocity.

Altogether, most of humanity left Earth for the heavenly world being constructed among the stars. Someone who arrives here by conveyor would find a mostly empty Earth populated by a few ideological holdouts, and a sky twinkling with alchemical lights.

10: Psion resonance causes a chaotic projection wave to take place. Briefly, all humans astrally projected, and then returned to bodies. Some 20% of people returned to their own bodies, another 60% returned to other people's bodies, and the last 20% were apparently carried away with the storm... and there are rumors that some number of bodies were inhabited by alien minds as well...

The population dropped by a few hundred thousand during the astral projection -- people who were driving at high speed, swimming, or otherwise reliant on someone else being conscious. More severe was the fact that 20% of the population was effectively comatose but not dead -- nor was there any clear reason for them to be unconscious. The issue seemed like it would be ideological, but ultimately it became practical: there's no way to keep one in five people on life support just in case they wake up. A few hundred thousand of the "coma" people were kept on life support due to special circumstances, but within a few months almost all of those 1.4 billion people died.

The actual projection itself took the form of a change in consciousness and disassociation more like a drug experience than anything else. Most reliable accounts say that it wasn't specifically a feeling of traveling from one body to another, but rather "fading" out of being associated with a given body, experiencing a moment of simply not "being" anything in particular, and then fading back into possession of a body, the same one or a different one. Memories were transferred with the consciousness.

About half of those that changed bodies found themselves in extremely different forms, meaning that a little over a billion people were, for instance, moved from an adult male body to an infant female body or the like. Some specific instances were particularly traumatic; there are three different occasions where those piloting an airline that crashed during the effects of the wave found themselves in a body that was far from the aircraft afterwards.

The social disruption was less severe than in other situations. There was rough period of hunger and recovery, but since only a small portion of minds crossed extreme distances, most people were able to return to something like their old lives. The actual disaster itself was too bizarre to really respond to, although in general pretty much everyone alive considers it a given that identity isn't tied to physical body anymore.

The lingering issue is that there are legitimate reasons to suspect that there has been some kind of alien infiltration in the process. Although millions of people went bodily missing in the catastrophe, most bodies were accounted for eventually. However, to this day many more people are still unaccounted for. With the scrambling of faces and names, it's impossible to be totally sure that a person is who they claim to be. The bizarre phenomenon would surely trigger a wave of strange conspiracy theories, but in the wake of the disaster there are signs of some kind of global management taking place, and even sober and rigorous security groups are concerned.

11: The wake of the storm disrupts all electronic devices, creating a world not unlike Rustic.

Standard social collapse disorder profile. Steam and powered reconstruction, long-distance semaphore messaging. Limited political breakdown because military-civilian cooperation was necessary.