Moroni explains that he is abridging the record called the book of Ether contained on the twenty-four gold plates that were discovered by the people of Limhi (see Mosiah 8:5-19; Alma 37:21-31), and that his abridgment does not contain a full account. The full account included important information concerning the Creation, and happenings among the people from Adam down to the time of the Tower of Babel.
We note Moroni’s recognition that a record of these things “is had among the Jews” (the Bible). Undoubtedly Moroni was also familiar with Nephi’s prophecies that the record of the Jews would have many “plain and precious things” removed front it (see 1 Nephi 13:26-29). Hence the person who would bring Moroni’s record to light in the last days would also “have power that he may get the full account” of those things on the plates of Ether.