The Godhead was a source of unlimited power created by the Alchemaitres near the end of time.
The Ministers of Grace separated the Thought Core from the rest of the Godhead and shattered the Godhead into shards that they then scattered through time.
After collecting the shards of the Godhead, the Master tried to reunite it with the Core, which was located in Chicago. The reunited shards of the Godhead acted on their own, trying to find the Core.
The pieces were brought together by Margie del Monsalvat, and the Godhead needed a mind to control it. Margie intended for it to be the Master's mind, but instead it chose the dead body of Father Sherrin. Under his control, it left Earth. (PROSE: The Duke of Dominoes)