(My reaction is that they were fallen angels because angels can shapeshift to look like humans and can likely disappear or appear because they have immortal bodies just like Jesus who walked through a wall as He had an immortal body. John 20:19. In my opinion when Satan & the fallen angels are thrown out of heaven and down to Earth, they will arrive in gigantic motherships to deceive the people on Earth into believing they were are creators and tell us we were made in their image so they will be shapeshifted to look like humans. And when they perform great signs lying wonders that look like miracles, many on Earth will be deceived by them and worship the Antichrist and his image and receive the mark of the beast in the right hand or in the forehead. This is my own opinion.)