What “Plain and Precious Things” did the “Great and Abominable Church” Keep Back from its Biblical Teachings?

In two unique chapters of the Book of Mormon, 1 Nephi 13 and 14, the prophet Nephi, writing during the 6th century B.C., relates what an angel showed him in vision about the future history of Christianity in Europe and the Americas.  One of the most salient features of his vision is a description of what happens after the Old Testament Jewish scriptures and the New Testament Christian gospel have been recorded and written in their uncorrupted form1 by Israelite and Jewish writers of the Old and New Testaments.  Over the centuries, as these records and writings coalesce into what is known today as the Bible2,  they are then adopted and accepted by Christians as canonical.  Thereafter, the Bible comes into the possession and control of what the angel and Nephi refer to as the “great and abominable church.”  The result is that the biblical message, formerly pure, becomes corrupted in the way it’s taught to Christianity’s adherents.  Specifically,  the church’s teaching is observed to be missing “many plain and precious things” which have been “taken away” or “kept back” by said evil church.  See 1 Nephi 13:26, 28-29, 32, 34, 40.