The Black Surfer was originally a regular Blackbody that was given to Vartu to keep his own souls in. He was able to use the soul of the Silver Surfer and combine it with the Blackbody in order to fight the Silver Skyriders. It was then that it became the Black Surfer.
It proved more than enough to take on the Skyriders, 12 inexperienced versions of the Silver Surfer. It was called back to Vartu when he could no longer risk losing his souls to the Skyriders efforts. When the Silver Skyriders attacked the Uni-Lord and Vartu, they used a the Blackbody to remove their power. But by doing this they created a vessel for the escaped soul of the Surfer. When Pradda Fol took the Surfer’s place in the Congregation of Finality, the Surfer combined the parts of his soul into the Black Surfer and was reborn, destroying the Black Surfer and taking all of Vartu’s souls into himself.
What was left of the Blackbody was sent to the Congregational and later used by the Uni-Lord to try to finish off the Surfer. When the Surfer defeated him, the Congregation died and the Black Surfer along with it.