As the 22^nd century draws to a close, mankind is in a sorry state. Conflicts are frequent as greed has driven us to the brink of global catastrophe. Nevertheless, corporate life goes on and shareholder expectations need to be met. Thus, in an attempt to circumvent laws that prohibit experiments on human DNA and fetal tissue, several major corporations find themselves in a race to discover creative ways to work around the existing legal issues, by modifying animal DNA to be more "human-like" (and thus a viable source for experimentation). The so-created "hybrid" DNA turns out to be a "close-enough" match for several medical applications. However, for a long time this process has been time-consuming and expensive, since each hybrid DNA has to be tailored specifically to fit one intended purpose.
This has changed recently! A new scientific breakthrough (invented, stolen, then patented twice under different pretexts by competing companies) allows cheap, safe, and efficient genetic modifications on a much larger scale. The modification introduces severe alterations to animal DNA that make it 100% compatible with the human genome. This new DNA manipulation technique provides the market with the "one size fits all" solution businesses have been waiting for. It is universally applicable, easily modified to the customer's requirements, and suitable for a wide range of tests with no need for expensive changes.
The idea is simple: Even though it is illegal to experiment on human DNA, to experiment on animal DNA that just happens to be genetically modified to look and behave exactly like a human genome is perfectly legal.
It may have taken a genius to develop the technique, but it certainly didn't take one to figure out that growing this DNA into an actual creature could practically create anything from perfect slaves to perfect soldiers. Consequently, when one of the remaining big global players expresses an interest to purchase just that, the two major competing companies in the field present their respective best efforts to deliver what the market asks for. As always, eventually one company is chosen over the other. But all is not said and done: The promised "hybrid" creatures still need to undergo testing.
As circumstance may have it, the customer just happens to have come in possession of a seemingly barren planet, that would be perfect for a field test. Even though it is in the habitable zone, it has a toxic atmosphere, and is thus of little value. No efforts have been made to investigate, let alone colonize it. The environment of the planet is believed to be too hostile to host life as we know it. Unless, of course, you add a little twist to that life. The corporation thus decides to go ahead and use this planet to test-drive this new, promising generation of human-animal-hybrids. If they manage to live up to expectations, the company producing these fine specimen would be chosen to deliver large numbers of robust and versatile T-Hybrids^tm for tactical operations, exploration, and terraforming purposes—thus putting smiles on the faces of their shareholders.
The experimental hybrid races are thus placed on said planet and (just to be safe) made to worship the human military as their Gods, whose orders must not be disobeyed. These Gods, however, are not exactly benevolent. They incite conflicts between the races to test their abilities. Yet, it is just then that the military experimenters realise that there initial understanding, that the planet was uninhabited, was wrong. The planet proves to be home to primitive, yet intelligent, alien creatures, representing a form of life we never even dreamed could possibly exist. In panic, the invasion force decides to cover their asses by nuking the population from orbit. However, their success proves to be incomplete, as many of the hardy alien creatures survive this first onslaught. So instead, the military invaders decide to make the best of the situation at hand, and pit their newly acquired hybrid races against the aliens to see what happens.
In the meantime, the other human company—the one that lost the contract for a lifelong delivery of their own version of hybrids—is not ready to give up so easily. They have learned the secret location of the project and sent their top covert agent to investigate. She is to either disrupt the ongoing experiments, or (preferably) collect sufficient blackmail material to regain the previously lost, lucrative contract after all. However, the agent's craft is discovered, and has an unfortunate encounter with a bullet. Heavily damaged, it crashes on the planet. While she survives the crash, her spaceship proves to be beyond repair. In this situation she is found and saved by some of the local alien primitives, who call themselves "Serai". She finds a way to communicate with the tribe, and thus learns of the atrocities committed against them. With no other way off the planet and her own resources stretched dangerously thing, she decides to divert from her original mission and help the natives. By raiding military outposts she hopes to secure some of the so desperately needed supplies for herself.
But politics is a bitch everywhere in the galaxy, and the Serai are no exception. The Serai worship the "three disciplines of science" (Manthor, Scani, and Buhaad) above everything else. They have a legend that some day, in their hour of great need, a supreme master of knowledge would decent upon their world to unite the three primary schools of science. This master would bring their people together and finally lead those of them who are worthy to a place among the stars. Only the unworthy would be left behind.
As fate may have it, all the major political figures of the Serai (the council of the three sciences) were killed during the previous attack. This leaves a vacuum of power and somebody ought to fill it. Thus a young, ambiguous Serai apprentice approaches the strange alien agent and asks sheepishly if he would be allowed to call her "the source of great knowledge". She accepts this title, unknowing that in doing so she just declared herself to be the second coming. So, instead of helping the Serai out, she is about to become the cause of a civil war.
Meanwhile a third, hidden power had lingered in the dark, waiting for their chance… The Serai are asexual. They reproduce by giving birth to a single child. However, this child is not Serai. Instead, their offspring are "elementals": sexual creatures of extreme heat (male) and extreme cold (female). When two elementals of opposite sex join, their "melting process" creates a new Sera. After that, the cycle starts anew. Unfortunately, both elementals lose all memories of their previous life in the "melting". As this knowledge can be scary, it is decided that it would be best to not tell the elementals the story of the "birds and bees". Plus, since all knowledge is sacred to the Serai, no knowledge may ever be shared with "lesser" creatures. Such a truth can thus never be passed on to an (as of yet) unworthy elemental by any true Sera, as this would be an act of blasphemy. As a result, for all the elementals know, they see that two of them at a time enter through a certain door and neither ever returns. They feel that they are just slaves to their Serai masters. And they decide that the recent attacks have given them a chance to finally break their chains and strike back. The children of the planet are thus on the eve of a horrible mistake!
Or in other words: this world is about to go to hell in a handbasket, and they who dare to enter in this game will have front-row seats!
The background story up to this point may remain unknown to the players. As dungeon master you may choose to reveal it bit by bit while the party progresses through your campaign—or not at all.