As the medieval church sought to gain wealth and power, it was led to make a compromise between paganism and Christianity, supplanting the word of Christ with allegiance to a human being—the powerful bishop of Rome. Without the Bible as a safeguard, people had no standard to distinguish between right and wrong and were at the mercy of a corrupt Church and clergy. What followed was an era of spiritual darkness foretold by prophecy.
During the 1,260 years of darkness, the word of God was nearly banished from the face of the Earth. Evil had full sway, with unthinkable crimes being committed and celebrated. Yet, God's light of truth is never fully extinguished. Throughout history, He has always preserved a remnant who are true to His Word.
To learn more about this era of spiritual darkness, read The Great Controversy by Ellen White at https://greatcontroversyproject.org/.