Power surmises that he became numerous figures from history, myth, and legend, and the Nine bred Lord Grandrith specifically to live out the destiny as foretold by The Undying God, which was, of course, the story of Tarzan himself. He also claims that Lord Grandrith was the individual who did some of the deeds and participated in the adventures of "Tarzan", when these adventures clash too greatly with established Wold Newton continuity.
Power hypothesizes that he became numerous figures from history, myth, and legend, and the Nine created Lord Grandrith specifically to fulfill the prophecy as foretold by The Undying God, which was, naturally, the story of Tarzan himself. He also asserts that Lord Grandrith was the person who executed some of the feats and participated in the escapades of "Tarzan", when these escapades conflicted too greatly with established Wold Newton continuity.