Sun Wukong stopped before the Endless Abyss, as he intended to transform the last bit of Immortal Primordial Force within his body into a new type of Primordial Force. This newly-formed Primordial Force shared some similarities with Chaos Qi, so Sun Wukong simply referred to it as Chaos Primordial Force.
This Chaos Primordial Force possessed a strong inclusiveness. As long as Sun Wukong converted all the Immortal Primordial Force inside his body into Chaos Primordial Force, it should be possible for him to transform whether it is nature's spiritual energy or Netherworld Ghost Qi, or any other energy, into Chaos Primordial Force in the future.
Of course, Sun Wukong had not verified this idea, but he had a strong premonition that it was likely the case. Anyway, whether it was true or not, he could simply absorb some Netherworld Ghost Qi to verify it after the transformation was complete.
