they aren't 'aliens' from another planet. they are Demons, sent to lie, kill and destroy.
How would a person from the 1st Century describe an 'alien' ??
REVELATION 16: 13,14
And I saw three unclean spirits like frogs come out of the mouth of the dragon, and out of the mouth of the beast, and out of the mouth of the false prophet.For they are the spirits of devils, working miracles, which go forth unto the kings of the earth and of the whole world, to gather them to the battle of that great day of God Almighty.