However at the start of book 6 Director Xine states that the four swords were implemented by the high men as a means to subdue the hostile personality developing within the black pearl.
I'm a bit comfused...The souls of billions created a gestalt personality within the Black Pearl, which became hostile to the beings inhabiting Purgatory. In order to subvert this personality, the High Men devised a means in which to subdue it by calling to powerful warriors across the land.
Heroes would always come, but even after every defeat the Black Pearl would emerge once again-- that is, until the Heroes of Pentawa arrived in Sorceria. It was this group of adventurers that altered the course of Purgatory, but even they seem to have failed.