I wrote a back story inspired by X-Com and I thought I'd share it here. Its rough and im intersested in seeing what you guys think and if you have suggestions/comments
Humans & aliens grouped into two factions locked in a millennia-long war which began when a group of explorers discovered a artifact in the center of the galaxy. When touched by an ungloved hand, the artifact released an energy wave which rippled throughout the galaxy. The energy wave had a strange effect on all organic life causing the cells in the vertebrae to mutate in what scientists are calling "Freeform Evolution". This mutation transforms the individual's physiology based on emotion, self thought and environmental interaction - including their moral choices and social interactions. The mutation somehow absorbs this and uses the brain's self projection to physically modify the molecular & cell structure of the subject.
In addition to aesthetic changes, whom the individual interacts with can also influence these physical changes. As an example, by associating with unsavory individuals, the group of individuals all appear to produce particular pheromones in a way to identify with one another. This indicated that "Freeform Evolution" is somehow interconnected with every organic molecule. These changes have changed the social dynamics of all the species in the galaxy except one - the elder race, who are known as the oldest species in the galaxy. They can take solid form but have not be affected by the artifact since they have evolved into higher forms of life - light energy. cannot interfere on this plane of existence.
Originally the protectors of the artifacts but this was forgotten over many millions of yearsThe humans are invading the Elder's abandoned planets in hopes of recovering several more artifacts which are told of in legends. Those who control all the artifacts can not only shape their own physiology and extend their mortality but also shape the universe. In response to the Human threat, other races have banded together to fight the Humans (and their allies) to destroy Humanity.
So Humans are the "bad guys" bent on taking over the known universe. Your species are the extraterrestrials, your mission is to do whatever it takes to conquer a specific planet (expansions could be extra planets, systems etc). Terrorize local populations, abductions as well as infiltrate the natives to achieve your goals. Unfortunately you're not alone and other alien factions have joined in to stake their claims or protect the locals from destruction. Scout for base locations, build your bases, resource mines, supply depots and more all in the aide of achieving victory for the species. Players must establish ongoing resource gathering, diplomacy, research, manufacturing and more.