Ouyang Yudu could have undergone Nirvana a long time ago, and if he had wanted to ascend, his innate abilities would have allowed him to achieve it much faster than Lin Shen.
But he had never undergone Nirvana because he feared that once he did, he might no longer be himself.
Originally, Ouyang Yudu thought that even without Nirvana, he could still accomplish much with the body of an Ascender; however, witnessing the battle between Lin Shen and an Immortal made him realize that, without undergoing Nirvana and becoming an Immortal himself, he was nothing more than a rootless duckweed, unable to truly establish himself in this cosmic expanse.
Lin Shen watched as blood-red threads of light spilled from Ouyang Yudu's body, forming a Nirvana Light Cocoon that enveloped him, yet Lin Shen's heart was somewhat uneasy.
He had long known there was something amiss with Ouyang Yudu's body, but what that thing inside him was remained a mystery.