"I have returned. After an eternity away from you all, Jack of Blades is Back!"
From the Void in the distant, distant past came three beings of nigh impossible levels of power. The Knight, the Queen, and the Jack of Blades. In the beginning, they sought total domination. And after they turned the earth black, the sky gray with smoke, rose the seas to flood the wastes, and warped the minds of the people until brother killed brother and children turned against parents. Only after of all of that did the people surrender.
From the ruins and tyranny a Hero named William emerged carrying the Sword of Aeons. He slew the Knight and the Queen in most Epic fashion, raising mountains and making valleys into the landscape by the blows struck. Only Jack survived, and even then, it was only his soul he sent back into the void that spawned him. William was to become King, but Jack was not yet truly defeated.
At some point, he returned in the form of a Mask that depraved people of the world wore and worked his will. In this way, he's struck a swath of destruction for generation after generation. The Oracle, a source of unbiased knowledge in the Fable world, had this to say about him. "He is no Hero. He is not even a man. When the world was a blur of fire and demons, when its soil had felt not the tread of humans and was filled with creatures only your worst nightmares could begin to suggest, even then was Jack old."
At last, Jack of Blades (as soul prisoned in his mask) was ultimately destroyed by Hero of Oakvale.