The moment Jacob touched the Primary Nightmare, his vision went blank, but he wasn't concerned because he was too familiar with this procedure.
When his vision returned, he found himself within a vast void that seemed to stretch endlessly, and after devouring so many fragmented memoires of Whiteness, he knew this was the Universal Void, Whiteness's birthplace.
However, this Jacob seemed slightly surprised because, unlike the fragmented spaces of the Void he had seen before, this place seemed complete, structured, functioning, and on top of that, real.
Lastly, what surprised Jacob even more was that this place was filled with unique lifeforms of the Universal Void, the Zodiac Beasts.
These Zodiac Beasts have countless forms, and many have been seen in Whiteness's fragmented nightmares and dreams, either hunting him or being hunted by him.
