Demons are NOT human. They are invisible evil spirits with various sizes and shapes.

God did in fact create everything (including Lucifer). Colossians 1:16 "For it was in Him that ALL things were created, in heaven and on earth, things SEEN and things UNSEEN, whether THRONES, DOMINIONS, RULERS, or AUTHORITIES; ALL things were created and exist through Him [by His service, intervention] and in and for Him."

AND
JOHN 1:1 In the beginning was the Word, and the Word was with God, and the Word was God. 2/The same was in the beginning with God. 3/ ALL THINGS were made by Him; and without Him was not anything made that was made.

We do know that the demons have rankings (like the military). Again in Colossians 1:16 "...things seen and things unseen, whether THRONES - DOMINIONS - RULERS - AUTHORITIES
King James version calls them "VISIBLE and INVISIBLE, whether THRONES - DOMINIONS - PRINCIPALITIES - POWERS

Ephesians 6:12 "For we wrestle not against flesh and blood, but against PRINCIPALITIES, against POWERS, against the RULERS of the darkness of this world, against spiritual wickedness in high places." KJV


Ephesians 6:12 "For we are not wrestling with flesh and blood [contending only with physical opponents], but against the DESPOTISMS, against the POWERS, against [the master spirits who are] the world RULERS of this present darkness, against the spirit forces of wickedness in the heavenly (supernatural) sphere." AMPLIFIED

The above scriptures destroy any notion that there are NO demons.

DEMONS - WHAT THEY ARE NOT -- If you think the demons are the "fallen angels", this can only be a personal opinion. There are some Scriptures that are not clear (like in the Book of Revelations), so everyone has their own opinion. However, as far as "fallen angels" go, check this out. These two Scriptures are quite clear. There is no room for opinions.

II Peter 2:4 "For God did not [even] spare ANGELS that sinned, but CAST THEM INTO HELL, delivering them to be KEPT THERE in pits of gloom TILL THE JUDGMENT and their doom."

Jude, verse 6 "And ANGELS who did not keep (care for, guard, and hold to) their own first place of power but abandoned their proper dwelling place--THESE He has reserved IN CUSTODY IN ETERNAL CHAINS (bonds) under the thick gloom of utter darkness UNTIL THE JUDGMENT and doom of the great day."

DEMONS - WHAT THEY DO -- Their job is to CONTROL you, to DEFILE you, to HARASS you, to TORMENT you, and to DRIVE you to DO, SAY, THINK, and FEEL things you wish you could eliminate from your life.

WHAT DEMONS ARE FROM THE MOUTH OF JESUS
Mark 7:21 - 23
21) For from WITHIN, [that is] out of the hearts of men, come base and wicked thoughts, sexual immorality, stealing, murder, adultery,
22) Coveting (a greedy desire to have more wealth), dangerous and destructive wickedness, deceit; unrestrained (indecent) conduct; and evil eye (envy), slander (evil speaking, malicious misrepresentation, abusiveness), pride (the sin of an uplifted heart against God and man), foolishness (folly, lack of sense, recklessness, thoughtlessness).
23) All these evil [purposes and desires] come from WITHIN, and they make the man unclean and render him unhallowed.

This is why in Mark 16:17 Jesus said to cast demons OUT