How many angels rebelled against God and followed Satan?
There is a strong indication that Satan was able to draw one-third of the angels into joining his rebellion. And that is what demons are: the angels who fell with Satan and came to be his servants on this earth.
Its tail swept a third of the stars out of the sky and flung them to the earth.
Revelation 12:4a
And we know from the use of the word “stars” in the book of Revelation that stars refer to angels.
