When we first meet the secret combinations in Mormon’s records, it is in connection with the information on the plates of Ether. At that time, Alma tells his son Helaman that as part of his responsibilities as the keeper of the records, that he should keep this information about secret combinations safe and not publish them:
Alma 37:21-22
21 And now, I will speak unto you concerning those twenty-four plates, that ye keep them, that the mysteries and the works of darkness, and their secret works, or the secret works of those people who have been destroyed, may be made manifest unto this people; yea, all their murders, and robbings, and their plunderings, and all their wickedness and abominations, may be made manifest unto this people; yea, and that ye preserve these interpreters.
22 For behold, the Lord saw that his people began to work in darkness, yea, work secret murders and abominations; therefore the Lord said, if they did not repent they should be destroyed from off the face of the earth.
Moroni follows that same pattern. He tells us that their oaths are there, but he declines to elaborate, for they are covenants that should not be had among men, even though they are among the Lamanites, and have already caused the downfall of the Nephite nation.