The Three Realms are not a place protected by gods and Buddhas, but a prison maintained by the "contract of heaven" - gods and Buddhas are "contract holders" and feed on the faith of all living beings; demons are "contract evaders" who are tainted as evil because they refuse to offer sacrifices; humans are the "sacrifice" of the contract and are sacrificed repeatedly in reincarnation.
Obtaining scriptures is not a "transcendence", but a ceremony in which Lingshan and Heaven join forces to restart the contract - Tang Monk's ten reincarnations are the "contract container", and the Eighty-one Difficulties are the "activation program". In the end, Tang Monk's flesh and blood must be used as a guide to bind the three worlds under the new contract.
