In Mormonism, sons of perdition are those who are permanently cut off from God and consigned to Outer Darkness. They are described as individuals who once had a perfect knowledge of Jesus Christ, received the Holy Ghost, and then willfully denied and rebelled against him. Because of their total rejection after full understanding, they lose all hope of forgiveness.
This group includes Satan and his followers from the premortal life, as well as a few mortals who commit the “unpardonable sin.” Most Mormons believe that very few people will become sons of perdition.