Ammon, Aaron, Omner, and Himni were the sons of Mosiah, a Nephite king. They were among the unbelievers and went about with Alma the younger seeking to destroy the church of God and lead people astray. While they were rebelling against God, an angel of the Lord appeared, spoke with a voice of thunder that shook the earth, and called them to repentance (Mosiah 27:8-14). They were converted and turned from their former course.
They declined to take the throne, choosing instead to preach to the Lamanites, the traditional enemies of the Nephites. They could not bear that any soul should perish, and the thought of any soul suffering endless torment caused them to tremble (Mosiah 28:3). Mosiah inquired of the Lord, who said that many would believe and that he would deliver his sons out of the hands of the Lamanites; Mosiah then granted their request (Mosiah 28:7). With no son willing to accept the kingdom, Mosiah was left with no one to confer it upon (Mosiah 28:10).
They taught among the Lamanites for fourteen years, facing imprisonment and affliction (Alma 17:4). Their converts included King Lamoni, Lamoni’s father, and others who took the name Anti-Nephi-Lehies. Thousands of Lamanites were brought to the knowledge of the Lord and taught the Nephite records and prophecies (Alma 23:5).
They had searched the scriptures, given themselves to prayer and fasting, and had the spirit of prophecy and revelation, teaching with power and authority of God (Alma 17:2-3). Mormon later compared the captain Moroni to Ammon and his brothers, calling them all men of God (48:18).