The twelve apostles taught the true teachings of Jesus as they supervised the growth of the Church of Christ. But the early Christians were severely persecuted for their beliefs, and one by one the apostles were hunted down and killed. Tradition tells us that the apostle Paul was beheaded by order of the Roman Emperor, while Peter was crucified upside down.
In their absence, the simple truths that had been taught by Jesus were rejected, altered or replaced with pagan and Jewish beliefs and ceremonies that had not been established by Jesus. In his wrath, Satan used deception to drive the Church into a state of apostasy and wickedness. As a result, Jesus stopped providing mankind with revelations and he took away the power of the priesthood.
Satan was so successful that the whole known world became his dominion. Pagan beliefs—such as the doctrine that God does not have a physical body of flesh and bone—began to dominate. And it was this false form of Christianity that the Romans adopted as the official religion of the empire in 324 AD. By then all miracles had ceased, for the true church was no longer to be found on earth.
Heavenly Father's glorious Plan of Salvation by which mankind can become Gods was entirely forgotten, and in its place came extreme pomposity, spectacular ritual, and impressive pageantry. By the fifth century AD, the Church had become so perverted that if Jesus had returned to earth at that time, he is unlikely to have even recognized it.
Hundreds and hundreds of years passed. The so-called Christian nations of Europe cemented the relationship between church and state, causing the secular influence over religion to increase even more. Spiritual darkness enveloped the earth. Culture, education, and morality became more primitive. It was a time rightly referred to as the Dark Ages.
Also from the creator of The Brick Book of Mormon: