The greatest curse Satan can implant on any nation is a secret murder cult to rob and kill to get gain. The Lord says that when these secret combinations began spreading among the Jaredites, the Lord gave to Gazelem (who is identified in D&C 17:1 as the brother of Jared) a sacred stone, or set of interpreters, through which God would reveal the identity of those who had secretly combined together to set up secret combinations based on murder and robbery. When the Jaredites were wiped out in civil war the Lord somehow had these sacred stone interpreters transferred over to Mosiah in Zarahemla and eventually the interpreters were hidden up with the gold plates and fell into the hands of Joseph Smith. What a fantastic history!
It will be noted in verse 16 that the Lord commanded Alma to keep all the secret oaths, signs and covenants of the secret combinations hidden away, so this curse would not spread among the Nephites and Lamanites the way it destroyed the Jaredites. However, we discover from Helaman 6:26 that the curse was spreading through the land, not because the record keepers had disclosed them, but Satan himself had revealed them all over again among his followers who wanted to set up the secret combinations again. As a result, Alma warns Helaman that the same curse which destroyed the Jaredites is now among the Lamanites and Nephites.