Five thousand years ago, the world of Lemuria was a utopia. At that time, Lemuria already had nine thousand years of recorded history behind it, growing, learning, and evolving. Lemuria had grown beyond war, hatred, and every sort of want, and it served as the capital of the nascent Galactic Republic. Its people were never entirely content -- they were always striving to improve themselves and the universe around them. Until they opened the door that was never meant to be opened.
Settri was the greatest scientist of Lemuria, a man who had mastered all of the existing sciences, and was inventing new ones. Finally concluding that he had exhausted the possibilities in this universe, he would try the ultimate experiment, and begin playing with other ones. He breached the barriers, not realizing the disasters that would follow.
As soon as the dimensional walls were opened, strange things began to occur. The normal patterns of probability broke down, and synchronicity began to rule. Conflicts broke out in a world that hadn't known conflict in generations. Even the weather, so long controlled, escaped that control and began to run wild, damaging much of the world. Finally, the sun itself, torn by the unnatural forces, rent itself asunder. Barely fifty thousand escaped the great Cataclysm, as it consumed the once-perfect world.
Settri was one of those who escaped, but he had been driven mad by the experience. Insane with power, he convinced himself that he had unleashed the ultimate forces of the universe, and that these forces had made him some sort of God. Well ahead of all the others, he escaped Lemuria, seeking a world to establish his power. He found it in a star system a few dozen light-years away, a planet that would be someday known as Earth.
He set himself up as the overlord of the primitive tribes he landed among, filling them with awe through his displays of "magic". Some of that magic was simply science, of course, but some was performed through his dimensional experiments. No one knows how he did all of it -- his control of this arcane art was extraordinary. But it was clear to the survivors of Lemuria that he would devastate his new homeworld as he had his old one, if he wasn't stopped.
The survivors of the cataclysm settled on Earth, destroying their starships to commit themselves to saving their new home. They chose a small uninhabited continent, and named it New Lemuria. They thrived there, using their still-advanced science to create a technological paradise. They were fecund, and quickly spread to the other large island nearby, which they named Atlantis. And throughout, they began to plan to stop Settri, and save this world.
He had not been idle in the intervening years. Having shortened his name to simply "Set", he had let the primitive humans build an entire religion around him, based in the city of Babylon. Periodically, he would lower the dimensional walls, to perform some miracle or another; he also began to teach a select group of humans how to do this. He was more careful than he had been back on Lemuria, but it was still clear: his "miracles" were slowly weakening the fabric of spacetime around Earth.
The original Lemurians finally acted when Set committed his ultimate act of arrogance: he used his extradimensional powers to construct an impossibly tall temple to himself. It was still in process when the word came in of what he was doing: as far as anyone could tell, he planned on using this tower to link the Earth and Moon. Not only was it impossible to create without the extradimensional power, it simply couldn't stand. It was clear that he planned to lower the barriers, and leave them down, permanently.
Lemuria attacked as quickly as possible. They dressed in black from head to toe, having learned that colored light tended to strengthen Set's "magic". War was unnatural to the innocents of Lemuria, but their determination was solid: they had to stop Set, or die as this world was engulfed just as their original one had been. It was costly; Set had equipped the humans with advanced devices, even some extra-dimensional ones that no one could fathom. But they were successful: Set was killed, and at the moment of his death, the unnatural tower came crashing down.
But it was too much to hope that the threat ended with Set's life. His surviving Followers regrouped and escaped, preserving what he had taught them very carefully. They prepared to counter-attack, and it was clear that New Lemuria was no longer safe, since the Followers of Set knew of it, and had access to much of his devastating power. So the Lemurians fully accepted their new role as protectors of the Earth. They moved into the human population centers, blending in with the populace; they even began to inter-breed. A small contingent was left, hidden, on Atlantis, but the bulk of the people went underground. They kept their eyes and ears open, though, for they knew that the threat of Set was not yet over.
Sure enough, some hundreds of years later, the priests and priestesses of Set resurfaced, this time in Egypt. Using their powerful magics, they began to build an impossibly powerful empire, oppressing the normal humans around them with their powerful "magic". The Lemurians, who had now begun to fade into legend, knew that their time had come again. They worked more subtly and secretly this time, but the effect was the same: they broke the power of the Followers of Set, freeing the humans. But this time, the Followers wrought a terrible revenge, using the last of their available power to cause the islands of Lemuria and Atlantis to sink into the sea. The Lemurians were homeless once more. They began to think of themselves as simply Those in Black.
Down the centuries, the pattern has continued. From the Roman Empire to the Third Reich, the Followers repeatedly gather their forces, pool their remaining knowledge, and take what opportunities civilization presents them for control. Each time, Those in Black appear, break the forces of the Followers, and then blend back into the populace. The power of the Followers has gradually weakened over the centuries, as they have slowly lost much of the advanced science that Set bequeathed to them. But they are still the most terrible force for chaos upon the Earth, and their danger is still quite real: each time they use their powers, they weaken spacetime just a little bit more.
You are one of the current generation of Those in Black. Your upbringing has been outwardly normal; indeed, by now the Lemurian blood has grown quite thin, diluted by millenia of breeding with the humans. But the mission remains: to protect the Earth against the evil forces that would risk everything in the name of power.
Those in Black are normally scattered around the world, with just a tiny number in any particular place. But rumor has it that the Followers of Set are about to make another attempt at power. You don't understand what they plan, but you have been drawn here, along with a number of your cousins. It is clear that the evil science is at work here -- the dimensional walls appear to be positively shattered, with many alternate realms crossing over into your own. Your task is clear: to find out what the Followers of Set are up to this time, and to stop them.
There are a number of strange factors at work here. One is Jeff Diewald, the now-deceased Con-Chair. Diewald is known to your people, as one who has long been drawn, unwittingly, into strange interdimensional occurrances. You've heard stories about him being transformed into the being known as Z during one occasion when the world was being invaded by another, feline dimension; as a black cat, he was drawn to the cause of Those in Black, and helped to close that rift. You suspect that he has been killed by the Followers of Set, for knowing too much.
Also, rumors are flying about alien presences on Earth now. The details are unknown, but the remaining detectors apparently traced two extraterrestrial vehicles landing in the past few months; contrary to most ordinary expectations, this is actually pretty rare. Those in Black have been cut off from the rest of the Galaxy for thousands of years. It would be very useful to have some idea of what the current cultural context is out in the larger world. Even knowing whether the Republic survived the fall of Lemuria would be interesting.