This whole issue to clouded in mystery, and unless we are very careful, what we say about it can easily become mythology.
There are those who try to get around the problem by suggesting that there was a pre-Adamic creation, and that Lucifer was the king over this world. Others believe that he was created along with everything else during the six days of creation.
I dismiss entirely the first suggestion, as there are no Scriptural grounds to establish the theory. Promoters of this teaching do have proof texts, but really they are flimsy and can be interpreted another way.
As for the second suggestion. I find this unacceptable also, because the inference is that God created Lucifer for the purpose of falling and causing the fall of man. This idea is dangerous and does not reveal God as a God of justice and love. It would mean that God planned for man to sin through Satan, and thus Himself would be the Author of sin. I believe that this issue should be left alone, for the simple reason that if God wanted us to know it would have been clearly revealed in the Bible. The very fact that there is no Scriptural evidence to prove the origin of Satan is warning enough that we should avoid it.
As I said above – we can easily slip into mythology unless we are careful. There are many things we do not know, which I believe are ‘the secret things of God’ – “The secret things belong unto the LORD our God: but those things which are revealed belong unto us … ” (Deuteronomy 29:29).
Lastly, I think that modern day Christians are too concerned about what the devil is doing, rather than being about the Lord’s work. You will notice that though Jesus encountered Satan and devils, He did not go looking for them. I am often reminded of the student in Bible College who had to write an essay on the topic Jesus and the Devil. He had three hours to do it. He got so involved in writing about the Lord Jesus Christ, that he was surprised when the bell went to tell him to lay down his pen. Realising he had written nothing about Satan, he scribbled at the bottom of his paper, Sorry, I have no time for the devil!
I believe it is more important to know Him who is the God of all eternity than trying to fathom out that which is not defined in the Bible. Instead of novelties, we should speak the clear revealed word of God. Too many are amazed at the wonderful, but often unscriptural, teachings of men. I think the subject of the origin of Satan is best left to the Lord. On that day we meet Him in person we will know even as we are known.