The Amulonites were descendants and followers of Amulon, a former priest of King Noah, who joined the Lamanites along with the Amalekites. Many of them held to the order of the Nehors and taught that God would save all men (Alma 21:4). When Aaron came to preach in the city of Jerusalem, which the Lamanites, Amalekites, and people of Amulon had built, the Amulonites were not converted (Alma 23:14).
The record states that while the Lamanites were already hardened, the Amalekites and Amulonites were harder still, and stirred the Lamanites up to greater wickedness (Alma 21:3). The Amulonites and Amalekites stirred the unconverted Lamanites to anger against the Anti-Nephi-Lehies and took up arms against them (Alma 24:2).
When the Lamanite armies fell upon the Anti-Nephi-Lehies, who prostrated themselves and would not fight, they slew 1,005 of them. Many of the attacking Lamanites then threw down their weapons and were converted, so that more joined the people of God that day than had been killed; but none who repented were Amalekites or Amulonites, who made up the greatest number of the slayers (Alma 24:28-29). Mormon explains why: those who have once been enlightened by the Spirit of God and then fallen away become more hardened than those who never knew such things, and their state becomes worse than if they had never received that knowledge (Alma 24:30).
Afterward the Lamanite armies were driven and slain in battles with the Nephites, and almost all the seed of Amulon were killed by the Nephites. The survivors fled into the east wilderness, seized authority over the Lamanites, and put to death by fire those Lamanites who believed the preaching of Aaron. This martyrdom turned many against the rulers, and the Lamanites began to hunt and slay the seed of Amulon. Abinadi had foretold that the seed of Noah’s priests would be hunted and slain as he had been put to death by fire, and the record states that they are hunted at this day (Alma 25:4-5, 8-9).