Satan was an angel and the choir director / music coordinator in Heaven if you will and he , due to pride , rebelled against God. Then he became the ruler of this world but is yet limited by God allowing or disallowing his actions and activities.
Just as in the book of Job, Satan goes before God as an accuser of the brethren and Satan has NOT been cast into hell yet. He actually occupies a space in heaven away from the Christians who have gone on.... and he will be cast out by Michael in the near future and then will go to hell.
All who do not accept Jesus as their Lord and Savior will die lost and spend eternity in hell. Christians are the ONLY one's with assurance of eternal life in Heaven after death, if they serve the Lord Jesus Christ.
Even muhammad never had the assurance of life in heaven as allah never promised and of course could not for he was not real, he was a moon god and as well the religion of Islam is a sham, although I do respect people and i feel that men may worship as they see fit, but i do not agree with other than true Christianity.
the only way to heaven is through Jesus and not sacraments, no 72 virgins will be waiting on anyone and etc.....
Satan is real and you will live with him in torment or Jesus in Heaven