I am currently DMing a solo campaign; the PC is a Half-Celestial Gestalt Paladin/Rogue.
Half-Celestials, or Seraphim (as they are called IMC), are directly responsible for the existence of mankind. The Emperor, as he is known, created mankind as a test of his power... the power of Genesis.
In actuality, the Seraphim are (in game terms) extra-terrestrial creatures who combine deity-like power with furturistic technology. They do not have divine ranks (and thus are mortal, and can be killed... eventually), but possess a multitude of abilities and powers. They scour the multi-verse, seeking out life and ways to cultivate it.
However, some Seraphim chose to oppose The Emperor, feeling their place in the multiverse should be its rulers, not its caretakers. As such, a great war began between two factions of Seraphim. Those loyal to The Emperor were victorious; as punishment, the opposing Seraphim were banished from Heaven (the Seraphim home world).
Not to be outdone, The Fallen descended upon "Earth" (styled in traditional D&D format) and began to plot their revenge. Using the natural resources of the planet, they began to form great Weapons of Mass Destruction -- (in game terms) Mecha. They also took the dominant race of the planet -- human -- and changed their biological structures to better suit their performance at specific slave tasks. Thus, the other races were formed.
With their weapons complete, The Fallen launched an all-out assault on Heaven. With the aid of their "new" technology, The Fallen nearly destroyed The Emperor's forces. In a last-ditch effort, The Emperor invoked Heaven's ultimate power... Light Speed. Indeed, the entire planet whisked off into the ether, its destination completely unknown. This action also stranded many of The Emperor's forces outside of Heaven's protection. So, both factions retired to the only planet within range: "Earth".
The Emperor's faithful were disgusted with the Fallen's treatment of the local races, and chose to champion the people against the tyrrany of the Fallen. Wars waged, lives were lost, and in the end... both sides were scattered to the four corners of the world. Much of their ancient technology lie dormant and broken all about the planet...
Segue to campaign present:
Aiden Spear, Prince of Spira (yup, it sure is *LOL*) learns that he possesses the blood of the Seraph when he suddenly transforms during his first outing as a soldier. He had arrived in a "new world" (much like the Columbus expedition, save that Aiden's people are more like Vikings and they landed in a tropical climate) where danger seemed to be around every corner. His people, terrified at the possible implications, soon see him to be their champion against the strange new world they face.
So, I have taken elements from all sorts of sources... Superman, Hercules/Xena, and Transformers (to name a few)... and created a hodge-podge of a strange new world where Aiden will struggle to learn more about his Seraphim past, discover ancinet technological devices and weaponry, and use what he learns and finds to protect his people against an unnamed army marching on his home town... and perhaps to return home.
