D&C 76

 In vision the Prophet Joseph Smith and Sidney Rigdon testified - 

"...this we saw also, and bear record, that an angel of God who was in authority in the presence of God, who rebelled against the Only Begotten Son whom the Father loved and who was in the bosom of the Father, was thrust down from the presence of God and the Son,

26 And was called Perdition, for the heavens wept over him—he was Lucifer, a son of the morning.

27 And we beheld, and lo, he is fallen! is fallen, even a son of the morning!"  (Doctrine and Covenants 76:25–27)

In commentary in the Millennial Star -

"By the way, the name “Lucifer” (verse 26) means “light bearer” or “light bringer” (common dictionary definitions). Continuing, we must be careful to read the last phrase of verse 26, above, exactly as it is. Some people inadvertently read it as “the son of the morning” rather than “a son of the morning.” The difference is important. If it were “the son of the morning,” it would imply that Lucifer was one of the highest in authority. Whereas “a son of the morning” implies that he was one of many who held authority and wielded influence in our premortal life. 

President George Q. Cannon, of the First Presidency, explained this. He said: “Some have called him the son of the morning, but here it is a son of the morning—one among many, doubtless. This angel was a mighty personage, without doubt. The record that is given to us concerning him clearly shows that he occupied a very high position; that he was thought a great deal of, and that he was mighty in his sphere, so much so that when the matter was debated concerning the earth and the Plan of Salvation, he was of sufficient importance to have a plan, which he proposed as the plan by which this earth should be peopled and the inhabitants thereof redeemed. His plan, however, was not accepted; but it was so plausible and so attractive that out of the whole hosts of heaven one-third accepted his plan and were willing to cast their lot with him. [Moses 4:1–4; D&C 29:36–37]. Now, the difference between Jesus and Lucifer was this: Jesus was willing to submit to the Father.” (In Millennial Star, September 5, 1895, pages 563–64.)

For me, this portion on sons of perdition in this vision is quite disturbing.