“In our language we use the name Lucifer for an angel who was in authority before God, who rebelled, fought against the work of the Father, and was cast down to the earth. His name means holder of light or light bearer, for he had gathered light by his heed and diligence before he rebelled. He has become a vessel containing only wrath and seeks to destroy all who will hearken to him. He is now enslaved to his own hatred. Satan is a title which means accuser, opponent, and adversary; hence once he fell, Lucifer became, or in other words was called, Satan, because he accuses others and opposes the Father.”1 Lucifer pretends to be an angel of light because he once was one of the Powers of Heaven. He was an angel of God who was in authority in the presence of God, who rebelled (T&C 69:6). He still feigns to that authority, and fools are still misled into covenanting with him.2See also SATAN.
1 T&C 158:7–8 Answer to Prayer for Covenant.
2 40 Years in Mormonism Lecture 5, “Priesthood,” 44.