The Bible mentions a wide variety of created spirits. One problem we have in knowing more about spiritual creatures is that the writers of Scripture had to use physical categories to describe spiritual realities. Another, more actual, problem is that we normally have little experience with spiritual creatures and so when we may think we are in the presence of angels of light they may actually be demons.
One defining characteristic of Satan and his minions is that they are liars. This is why it is so important in our thinking about spiritual creatures and events to seek only to know what is true because truth only comes from God.
There is a fundamental division between those created spirits who have chosen to serve God and those who choose to follow Satan. The lower ranks of those who follow Satan we call demons. The New Testament also tells us of powerful beings, apparently produced by Satan, that are described as frogs, dragons, two beasts, a false prophet, and a reigning prostitute.
On God’s side, in addition to angels, there are archangels, elders and seraphim. Angels act as God’s messengers. Archangels also act to bring God’s messages to people. They also have a role in the destiny of nations and wage war against the satanic spirits. The elders lead worship in heaven and may have other roles. The seraphim, with their multitude of eyes, appear to have the job of overseeing God’s physical creation.
On earth, I believe we are in the midst of a vast spiritual warfare. Satan’s intent is not just to cause problems for people but to bring physical and spiritual death to as many humans as he can. Were it not for the purpose of the Father, the work of Christ and the Holy Spirit, and the obedience to God of the angels we all, without exception, would be doomed to eternal death.