Where do demons come from (Not he Christian concept)?

Demons, ALL demons, are created from the imagination of humans.

Demons are not "fallen angels". "God spared not the angels that sinned, but cast them down to hell, and delivered them into chains of darkness, to be reserved unto judgment;"

So fallen angels are not demons. The spirits of people who have died are bound in the heart of the earth, Hades because man was given dominion over this world and no other.

In Genesis 6 we read of 'sons of God' who had sex with the daughters of Adam's descendants and giants were born unto them. They became legendary for their strength and capabilities. These died in the flood, but after the flood it occurred again.

Like Adam (also a son of God [Luke 3:38] these 'sons of God' had a spirit, but we don't know about their dominion or the disposition of their spirits. The spirits of their offspring may not be bound in the earth since their patriarch was not from earth. Their spirit may not share the same disposition of their patriarch because they're the offspring of women. So in death, their souls may be the demons that seek embodiment and influence those who engage in Satan worship, Wicca and Shamanism, eventually taking over their body to themselves.

The whole point of demons in whatever cultures believe in some form of them is that they were never human spirits... demons are seen as malevolent non-human beings.

From the imaginations of human beings. Demons are imaginary.

Demons are fallen angels. They can sin like how humans can sin. And turn away from goodness. Spirits is another term for ghosts. They can be of good people and bad people, their energy that remains on earth.

It sounds like you don't want the truth. The truth is that if you believe in demons then you have to believe in God and the Bible and everything that it teaches and all Bible prophecys.

Revelation 12:9 So down the great dragon was hurled, the original serpent, the one called Devil and Satan, who is misleading the entire inhabited earth; he was hurled down to the earth, and his angels were hurled down with him.

Please realize that demons are a religious concept.

So: we know that you do not want us to explain the Christian concept of demons.

BUT...we are left not knowing which religious concept of demons you WOULD like for us to explain.

Muslim?

Jewish?

Hindu?

Buddhist?

Greco-Roman?

Shinto?

etc.

they probably come from satan

Human imagination.