Son of Perdition
An angel can fall from grace only by being cast out of Heaven (see 2 Nephi 1:9). When an angel falls, he becomes a devil. For these, it would be better if they had never known Christ, for they have decided to crucify Him anew. After having had the holy spirit make great things known unto them, they have turned against the Lord by their knowing rebellion against Him (see T&C 69:7). They are sons of perdition, and the Heavens weep over them (see T&C 69:6–7). These are they who know the battle is and always has been the Lord’s, and they either align themselves with Him or against Him.1See also UNPARDONABLE SIN.
1 “2 Nephi 31:14,” Aug. 26, 2010, blog post.