The being known as Cain is the first human child born to Original Miang after the Eldrige crash, on the beaches of Kadomony. He is supposed to be the Ultimate being, possessing power far beyond normal humans and surpassed only by the Chosen of the Wave Existence (the Contact, in other words). His goal - when boiled down - is basically an extention of Miang's; he is supposed to protect humanity for its ultimate purpose in the revival of Deus, and generally make sure the human race thrives until that time comes. So in the beginning, he created the religion and myths of Solaris in order to control the people that resulted from both Miang and Elly. However, when Abel and Elly opposed this religion and rebelled (whether they caused others to rebel - therefore splitting Solarians and Lambs for the first time - or not isn't clear to me at this moment), Cain killed Elly, and then probably Abel.
Occupation: Emperor of Solaris
At the beginning of Episode IV (year 9164) Cain gathered his followers and built Etrenank. It rose to the skies, and seperated Solaris from the 'other' people in the world. This is the final transition to what we see of Solaris during the present, and the surface dwellers (called 'Lambs') became not only lower life forms, but also slaves.
Several centuries later, after Sophia's death, Cain came into contact with Krelian, probably at Miang's prompting. Cain agreed to aid Krelian in his mission under the impression that it would help the people rather than herd them to their deaths as the Ministry wished. In repayment, Krelian extended Cain's life, though later it was necessary to clone him in order to promote his survival.
Over his lifetime, Cain seems to have gained considerable sympathy for the people under his control - both the Solarians, and the land-dwellers. It hardly shows in his actions, although his original motive in helping Krelian was to save his 'children'... his only visible effort is his attempt to stop the Gazel Ministry from using the Gaetia key on the second disc of the game. That is quite admirable, and we can't forget his attempts to fix things through Shitan, either. He may be a being od Deus's creation, but it looks like he managed to break free of his program.