Ages ago, there were eight Semi-gods known as Ashta Vasus. Once, out of sheer greed, they wanted to steal Sage Vashista's cow and the youngest of them, by name Prabhasa had stolen the cow.
Sage Vashista was enraged at this and cursed them to be born as human beings upon the earth. When the Vasus sought to be forgiven, the sage relented and laid down that the seven Vasus could live only for a few hours upon the earth but the Prabhasa was to lead his entire life upon the earth.
These Ashta-Vasus were the babies born to Ganga. The seven Vasus were thrown into the river and Prabhasa was the only survivor.
Ganga narrated this episode to Shantanu and disappeared after promising him that she would hand over Prabhasa to his care subsequently.Satyawati:
Satyawati was originally called as "Matsyagandhi". She was the daughter of King of fisherman 'Dasaraja'. Matsyagandhi used to work on the boat to take the passengers from one side of the river to the other.
Although she was not from very high cast or royal blood but she was very beautiful. Once Sage Parashara got into her boat to cross the river, and he blessed her with his love due to which Matsyagandhi gave birth to a baby without any pain. Sage Parashara took the baby and said he will be a great saint and in very critical time he will help you, but now I have to take him with me to educate him.
He blessed Matsyagandhi that she will be the queen of a big kingdom. He also blessed her that even though she is a daughter of a fisherman she will small like a flower. Her aroma will be sensed from even 100 mile away from her. She is another important character in the roots of Mahabharata