Complex sentence: This man was not elderly, but appeared to be King's own physical age (which was arrested due to vampirism) and was not a vampire (which would arrest his age) as this story predates the return of vampires.
Split into simpler sentences: This man was not elderly, but appeared to be Kings own physical age (which was arrested due to vampirism). He was also not a vampire (which would arrest his age) as this story predates the return of vampires.