In satan's rebellion in heaven, he drew with him a great multitude of lesser angelic beings. Revelation 12:4 His tail drew a third of the stars of heaven and threw them to the earth. . .

         These are called  'the devil's angels'  Matthew 25:41 Then He will also say to those on the left hand, ‘Depart from Me, you cursed, into the everlasting fire prepared for the devil and his angels:

                  These unconfined wicked spirits are under satan's kingdom and dominion. They are his subjects and are so numerous as to make his power seem practically unlimited.