The following is a rough adaptation of the setting of the 27 Survivalist novels by Jerry Ahern (actually, more precisely, of the novels from about book 10 to book 21 or so), and as such, contain some spoilers.
These books are available at reasonable prices via Peanut Press.
In a universe where the present-day Netherworld juncture opened about 15 years earlier, in the early '80s instead of the mid-'90s, a somewhat extremist Jammer faction hit upon the perfect plan for destroying the world's feng shui sites--nuke 'em! They smuggled Architect particle beam technology back in time to Soviet scientists who were Jammer sympathizers. Thus bolstered by this particle beam, which could supposedly destroy nuclear missiles right out of the sky, the Soviets launched a nuclear war.
In the conflagration that followed, 95% of the world's Feng Shui sites were
destroyed, and the entire power structure that the Ascended had worked so hard
to maintain was thrown into a shambles. The modern-day-juncture and future-juncture
portals to the Netherworld are permanently closed, and the Architects' future
is wiped out by critical shift. (Netherworld-hopping survivors in the future
find themselves citizens in one of the underground cities--with nothing to do
except to live out their lives there, with no netherworld gateway
to use.) What's worse, the destruction of these Feng Shui sites had an unexpected and remarkable effect, several months later--the destabilization of the planet's chi flow led to a total ionization of the atmosphere, causing a wall of fire to sweep across the globe with the sunrise. Well over 99% of the world's population was killed.
Five hundred years later, as the earth begins to recover, survivors of this second conflagration emerge from underground cities or return on cryogenic-equipped space shuttles placed on a deep orbit. The space shuttles contain mostly scientists and genetic material intended to recreate lost plant and animal life, but also contains a few people who make up the last vestiges of the 20th-century Ascended faction, who are eager to rebuild the power base they had lost.
However, both the Ascended and Dragons factions still survive on the earth, albeit in changed forms. There are several major and any number of minor redoubts and shelters that survived the 500 year test of time.
In South America, a large underground city called The Complex was built in
the late 20th century to provide safety to escaped Nazis and their families
in the event of a nuclear war. Fortunately for all concerned, it worked--however,
there were some Dragons in the mix (perhaps the kids of laterally-reincarnated
Secret Warriors), and
shortly after the reemergence, the Nazi regime is overthrown in a mostly-bloodless revolution.
In China, three sealed cities were created to keep the Chinese people safe. Only two were completed in time; the whereabouts of the third is unknown. One of these cities manages to preserve a civilized Chinese culture; the other has reverted to a more barbaric state characterized by nomad raiders and a nuclear-missile-worshipping death cult.
The same solar radiative effects that cause the Aurora actually caused the ionization and burnoff and its air-sapping aftereffects to miss settlements north of the Arctic Circle entirely. A peace-and-knowledge-loving Icelandic culture managed to survive for five hundred years.
Unfortunately, two factions of the cold war Soviet Union also survived. One, an underground city in the Urals, was responsible for much mayhem after the awakening, as they tried to conquer the world under the command of a powermad survivor (via cryogenic sleep) of the 20th century. The other, an undersea city, carried out its own raids and wars against an American undersea city (Mid-Wake) through those five hundred years, blissfully unaware that anyone on the surface had survived.
The last surviving vestige of the "true" United States of America was Mid-Wake, an undersea research base hastily converted for long-term survival between the nuclear battle and the atmospheric burnoff. Like the Soviet undersea city, it has been unaware of survivors on the surface until shortly after the space shuttles' return and general re-emergence. Midwake is also the last greatest holdout of the Dragon faction, having somehow managed to avoid taking on any major Ascended officers during its establishment. Midwake is notable for having perfected the most advanced medical procedures currently available on this new world, including a cure for most forms of cancer.
There are other, minor redoubts and retreats that didn't feature too prominently in this new world, including a second Nazi redoubt in the eastern USA where the citizens were kept in blissful ignorance in a 1950s-Americana-styled settlement, a retreat of the wealthy with a dreadful secret, and a French survival base that was understocked and whose survivors had to emerge prematurely, subsequently losing civilization and mutating into a race of more stocky, thicker-skinned people resembling cavemen.
There is also the Retreat of John Thomas Rourke, the novels' central character, and his family, which is important enough that it would be covered separately, as an adjunct to a Rourke writeup.
All of these mentioned redoubts either are or have Feng Shui sites associated with them. The return of these Feng Shui sites, and the regrowth of others, is what has been responsible for the recovery of the world from its oxygenless scorched state.
So far, no Netherworld portals have opened up--but then again, almost nobody currently alive would even know what they were if they did...