We do not know the names of these four bound angels. Christ the King has bound them there—for nothing happens apart from him. Angels are “all ministering spirits sent out to serve for the sake of those who are to inherit salvation” (Hebrews 1:14). “All” includes these four bound angels. On the point of their subservience to Jesus Christ, it is immaterial whether these are good angels or fallen angels (i.e., demons). Jesus Christ has “bound” them, meaning that they are not free to cross the River as they please but need to wait until Christ releases them.
14 saying to the sixth angel who had the trumpet, “Release the four angels who are bound at the great river Euphrates.”