Thanks for your question.
Isaiah 14:12-15 is the only portion of the Bible that talks about "Lucifer”. Who is he? The context will tell us. See 14:4, this chapter is a "proverb” the subject of which is the king of Babylon not a fallen angel. Note v.11, v. 16 ("the man” not an angel), v.19, and v.22 (still talking about Babylon). So, Lucifer, in the Bible, is the King of Babylon not some rebellious angel.
I hope you have found this helpful.