What are bad angels?

McClintock and Strong’s Biblical Cyclopedia is very helpful here. In Volume 2 page 883 it says the Hebrew word translated as dragon “seems to refer to any great monster, whether of the land or the sea., being indeed more usually applied to some kind of serpent or reptile, but not exclusively restricted to that sense. When referring to the sea it is used as a parallel to ‘leviathan (as in Isaiah 27:1… When we examine special passages we find the word in Genesis 1:21, of the great sea-monsters, the representatives of the inhabitants of the deep.”

From this explanation it is clear that the word dragon was used in a general way to describe various large land or sea creatures. It is not used in the way we might picture a dragon of mythology.

In the New Testament, the dragon is only found in the book of Revelation. There it is described as having seven heads, ten horns, seven crowns on its head and a tail. (See Revelation 12:3, 4)  However, it is clear that this is meant as a symbolic representation of a great worldly power. In Revelation 12:9 the dragon is called Satan to show that entity is his institution.

There is no actual creature as described here. God’s purpose in creating this imagery was to describe how Satan has endeavored to counteract the plan of God. Satan’s goal, as described in this chapter, was to destroy the true church, the woman mentioned in verse 6. This is a complex chapter full of powerful imagery.