Once there was a very powerful witch. upon finding her husband cheating on her with another woman, she turned the man into a snake and he slithered away. Now the witch, taking some pity on the broken-hearted woman, gave her a choice. Did she want to die right then or did she want the witch to make HER a witch with the promise that she would serve her for all of time. The woman chose to become a witch. One day, after searching long and hard, the mistress found the snake and with her new witch powers, turned him human again. However, she didn't get the spell quite right and the man kept shifting from snake to human, until finally he was able to control it. He became the original shape-shifter. They eventually ran away together and had many children. Those were the first pure-blood shape-shifters. The mistress and the husband were never found by the original witch although she searched for them.
* The born do not know what form they will shift into until it happens for the first time. Although, there IS a prophecy of a pure blood shifter born of the full moon with the mark of ______(?) It is said that he, and he alone can shift into ANY form at any time. His blood also happens to be a cure and he is completely immortal.