6000 years later a nomadic tribe of mostly humans found one of the secular repositories of magic and technology (mostly technology), called the Diamond Vault by Fourth Civilization archaeologists (the records were kept on engraved slabs of synthetic diamond). These people settled near this Vault and founded a small kingdom. They used the slabs as decoration first, until a half-elf recognized the symbols on them as writing ~1500 years later. She used the knowledge on these slabs to ascend through the ranks and become first the queen dowager, then after her human husband died and her child was still way too young to rule, the queen regent. She passed on the importance of this knowledge to her descendants, establishing a line of scientist monarchs, and the greatest empire of this age. In 1000 years this empire conquered the entirety of the continent and found a second vault, that one offering little in the way of technology but being packed full of magical knowledge.

In the next 1500 years this Empire was transformed into the Ascendancy, an oligarchy ruled by the Ascendants, people who successfully combined magic and technology in ways not nearly approached by the Fourth Civilization or the Giants before, and only seen during the First Civilization. One continent was turned into a nature reserve, and another was left untouched and unexplored for reasons still unknown.

The Ascendant technology made much of the previous technologies obsolete. Mining and agriculture ceased as materials were summoned directly from other planes and transformed into never-before-seen forms. Cities were constructed of a white slightly-translucent stone that was unbreakable when exposed to magic, people were served by magic-powered automatic servitors, information was stored and accessed on black slabs - some of which even capable of speaking and understanding what they are told, and a degree of thinking as well - and some people have even left the planet. The overwhelming majority (99+ percent) of people had magitech implants, improving their mental and physical faculties and arcane capabilities beyond anything that was seen since the First Civilization left this multiverse. They were said to rival the gods in power.

Two features of this age became important later on: On what is now called Golem Island, a technological development facility experimented on fully autonomous and self-replicating servants with minimal supervision. And as the civilization was extremely hungry for magical power, a new type of power source was constructed on the southeastern corner of Boreia that combined automation, power from certain elements in the crust, and arcane transmutation circles to empower the aether.

This led to the final collapse of the civilization. An oopsie in the aetheric reactor released a cloud of magic-infused radioactive particles that drifted over to Golem Island. The Island was evacuated and the reactor was covered in a dome of rock ~2 miles high (known to the Fourth Civilization as the Dome Mountain), but the technological development facility on Golem Island was left running. In the resulting power crisis recovery of that facility was a low priority which was, in retrospect, the worst decision of the Third Civilization.

The cloud altered the base programming of the experimental servitors, making self-replication and self-improvement their #1 priority. In 20 years the island’s resources were nearing exhaustion and the automatons began cannibalizing each other. In 30 years their cognitive improvement reached the point where they realized that this was unsustainable. 35 years after the reactor explosion automaton barges reached the coasts of the nearby continent.

In 75 years the Third Civilization was reduced from a globe-spanning empire of ten billion souls into maybe a million or two people huddled inside shield domes plus another million refugees on other planes protected by the Fae and the Primordials.

Working secretly, some of the Ascendants developed a weapon of last resort, essentially a magitech EMP. When the automatons breached a shield dome that was thought to be completely impenetrable, this remained their only choice. The EMP needed every bit of magical power that the civilization could muster, so refugees were ported back from the other planes too to power it.

Then the weapon was fired.

Every active magitech device on the Material Plane and the Inner Planes fried itself and died, except some that were shielded by an energy shield or miles of rock.

90% of the surviving people died instantly, their bodies being dependent on their implants. They were the lucky ones.

9% of people only had minor brain implants, mostly the standard hippocampus enhancement that took over their long-term memory. They reverted to the level of pre-verbal infants, only remembering a few small details that their organic hippocampus still bothered to store. Some of them even survived for more than a few days. A fraction of these people were children whose organic hippocampus was still active enough to let them live into adulthood.

1% of the people were unimplanted for one reason or another (too young, allergic to the implant, etc…). They spent the remainder of their miserable lives ensuring that sapient life survived. It is them who are to thank for the Fourth Civilization.

An automaton on Golem Island was testing a personal shield in the depths of a bunker. It was a comparatively simple machine, a Constructor, which is why it was chosen as a test subject. If the shield hadn’t worked, it wouldn’t have been a great loss. When the Pulse arrived, it destroyed every other automaton in the room which fell down onto the floor, their artificial mimicry of life cut short. The Pulse penetrated the shield too but was weakened by it, wiping most directives from the Constructor’s mind except the most basic ones hardwired in its brain. It detached the useless shield module from itself, disassembled the deactivated automatons in the room, then slowly and methodically began to build a slightly improved copy of itself. (These eventually evolved into the Golemkin, which are what the Warforged are called in this setting. They are peaceful but isolated by two groups of less-sapient self-replicating ships patrolling the sea surrounding their island, known as the Hungry Sea.)

And this led to the Fourth Civilization. The Ascendants who built this final weapon were in contact with the gods and reached an agreement with them before the weapon was fired. They were made Archons who then descended among the surviving mortals in secret and took samples of their bodies. Then with the help of Fae tree-shepherds and their own knowledge of magic, combined and copied the genes of the people and planted People Trees all over the world. In a few decades, they bore fruit, disgorging functioning adults with no real memory except the skills they needed for survival.

The Gods, Fiends, Fae and Primordials then convened for the first time since the end of the Soul War, and signed the Second Divine Concordat: Communication between Gods and mortals became more open and Gods were allowed to contact mortals unprompted. But there was one important stipulation: No being from outside the Material Plane might reveal information about earlier civilizations that mortals don’t already know. In addition, the Fae and the Primordials were allowed to create new mortal races alongside some other gods who didn’t do so after the Soul War, leading to the birth of the New Fey (e.g. satyrs and centaurs) and other races originating from the Fae and the Shade, the Genies, the Tabaxi, various birdfolk, the Tortles, and the Kobolds.

The New People came to Yphilios with no memory. While the parts of the 1% who survived the Sacrifice and were capable of speech tried to pass on their knowledge, barely any of that remained; it is estimated that only 0.1% of the vocabulary of modern languages originates from the language of the Third Civilization. Some information survived in oral histories, including the fact that the new people were the Fourth Civilization on the planet.

Still, these New People were not any less intelligent than their genetic donors. Witnessing the ruins of the Third Civilization (before they fell into complete disrepair due to not having any more magic keeping them whole) and hearing some strange older people make sounds with a distinct pattern to it spurred them into mimicking these behaviors, attempting to build structures similar to those ruins and using the same kinds of sound patterns to communicate. In addition, the gods themselves shepherded their people, subtly nudging them towards new technologies and revelations. The Fourth Civilization sped through the hunter-gatherer phase in scant 4000 years, establishing their first permanent settlements around 6000 years before Auberentian Reckoning.

The Third Civilization is the first time sapient organic life has evolved in this multiverse. The First Civilization came from another multiverse 30 million years in the past and left ~12 million years ago to another multiverse.

The Second Civilization was made of pure spiritual energy, evolved from the echoes of the First Civilization's souls around 9 million years ago (from the game's perspective); they could only manipulate the physical realm by possessing some animals. (Their favorite targets were simian creatures because of their useful limbs.) ~5 MY ago they found the natural pathways to the outer and inner planes plus the Feywild and Shadowfell-equivalents where their spiritual energy could embody without having to possess creatures and left. Currently they are known as gods and high-ranking celestials, archfiends, archfey, and the highest of the primordials.

And then ~2 MY ago those simian creatures that they liked possessing started evolving true sapience and sentience, climbed down from the trees and started walking on two legs, etc. Some groups of these beings (basically Homo Erectus) even made their way into the more friendly inner planes (the plane of Earth and the plane of Water), the Feywild-equivalent, and even the Shadowfell-equivalent.

As their society and culture evolved, so did the complexity of their brains (also spurred on by the use of fire which started on the Material Plane by the group that would evolve into Homo Sapiens Sapiens). The Second Civilization entities noticed that after death their more complex neural patterns didn't dissipate but instead passed on into the outer planes they inhabited, empowering them enough to affect changes on the Material Plane.

This sparked the Soul War, ~500 000 years ago. The Second Civilization entities on the Outer Planes were divided on how they should proceed with these new creatures. Many saw them as creatures similar to the First Civilization whose spark of sentience eventually led to the evolution of the Second Civilization, and as such they considered them peers worthy of respect (or at least free-willed creatures that might end up making good allies or powerful servants). Others just saw them as a convenient power source that needs to be captured and harnessed.

This ideological split led to the groups currently known as the Gods and the Fiends. The Primordials and the Fey were initially neutral in the conflict. The war raged on for 300 000 years, using the Material Plane as the battlefield and many of the early hominids as pawns. When it rippled into the inner planes, the Primordials and the Fey tried to play peacemaker but the differences between the gods and fiends seemed irreconcilable. After long debate they joined the war on the side of the gods.

In response the fiends started developing weapons capable of massive multiplanar destruction. The gods were willing to fight to the bitter end, but the Fey-Primordial alliance offered a compromise that was acceptable to both parties. The war ended with the victory of the gods but the fiends were allowed to build three thrones for themselves, and those who sit on the thrones would have the powers (and responsibilities, and limitations) of a god. (These were the Throne of Tyranny, the Throne of Corruption, and the Throne of Destruction.)

This was also when the first Divine Concordat was signed, severely limiting the direct contact between the outer planes and the material plane, and limiting the powers of fiends and celestials. (Elementals and Fey got a special exception since their planes are more closely-linked; they are capable of entering the Material Plane uninvited but their power there is only on the level of a mortal.)

Part of the Concordat was also the reconstruction of the Material Plane and the inner planes; gods, fey, primordials and even fiends were allowed to create new sapient races (with an ever-evolving set of limitations, e.g. after the creation of dragons they limited the maximal size and lifespan of the new races, and so on). This is the start of the Third Civilization in its earnest.

For ~150 000 years most races lived as primitive hunter-gatherers. But giants who evolved to colonize some of the more inhospitable regions (that were also affected by the magical fallout of the Soul War) had much longer lifespans, and this helped them develop their magic and technology. When they saw that the smaller races also started developing technology similar to their own, they knew that they wouldn't stop, so the Cloud Council decided to conquer them in order to prevent them from becoming a threat. This started the Age of Giant Kings ~50 000 years ago, with most humanoid settlements on the Material plane and the elemental planes being ruled by a fire giant or ice giant in the name of their cloud giant emperors.

This didn't last too long however. The cloud giants required tribute, and the fire and ice giants, wanting to curry favor with the cloud giants began teaching magic and technology to the small ones. This was forbidden by the cloud giants, per se, but they ruled so distantly that this was rarely enforced. The small ones organized resistance cells and began teaching these technologies and magic to other settlements whose giant king didn't do so. Then ~30 000 years ago the organized resistance achieved their first success, slaying one of the cloud giant emperors who ruled over the continent that was the ancestral homeland of the humans.

The next couple of decades were a series of rebellions, ending with 90% of the giants dead. The smaller races were aided by the fey, some giants who were sympathetic to their cause (mostly fire and ice giants), and some rumors say that even the gods helped them since the giant rule was uncomfortably similar to what the fiends wanted.

In the end the Cloud Giant High Emperor enacted the Curse of Forgetting on the world: everything that the giants knew would be forgotten and nobody would be able to re-learn it for 100 generations. He warded his own palace and close circle of advisors but unbeknownst to him one of the advisors was a rebel and he sabotaged the wards, leading to not only the smaller races but also the giants forgetting their magic and technology. What the High Emperor didn't account for was that the smaller races had their own homegrown technology and magic too, so the Curse of Forgetting completely backfired, making the smaller races the dominant people on the planet. This ended the Great Giant Civilization overnight, with the remaining giants retreating to the elemental planes or the most unhospitable reaches of the world. With Giant lifespans being much longer than those of the smaller races, their 100-generation curse also lasted much longer; they only began reclaiming their knowledge well into the life of the Fourth Civilization.

The Antique Period of the Third Civilization started with the First Bronze Age, during which people were unable to learn iron working or stonecutting, those being technologies that the Giants taught them. So this age was dominated by small settlements of wood, clay, and bronze, with bronze working, woodworking, and pottery being technologies they knew even before the giant conquest.

3000 years later the shorter-lived races suddenly found themselves able to invent ways to cut stone into shapes more complex than axe-heads and knives, and even smelt that elusive iron. The longer-lived races followed in a few millennia. For the next 3500 years this civilization developed similarly to civilization on Earth, but their reliance on magic led to some differences (i.e. they never discovered gunpowder or steam power; that is a technology unique to the Fourth Civilization).

At the end of this period the planet was dominated by three superpowers with ever-shifting alliances between them, locked in a cold war.

This cold war heated up at the end of that period, and the use of powerful arcanotech weapons led to an increase of volcanic activity which pushed the planet into a centuries-long volcanic winter. Crops failed, trade faltered, and starvation caused a population collapse. Some technology was preserved in religious and secular institutions but the surviving population was reduced to iron age levels. It took the climate millennia to stabilize and allow the population to start increasing again.