First, let's understand the MEANING of the word 'alien': Websters defines 'alien' as"other, foreign, not natural; strange, of aliens, foreigner, a foreign-born resident who is not naturalized, a hypothetical being from outer space."
The KJV uses the term 'alien' 5 times and it is always in the meaning of "foreign, foreighner, a foreign-born resident who is not naturalized".
The NASB uses the same term with the same meaning 46 times.
Although the word 'alien' is not used in the book of Revelation, it COULD be understood that the creatures of terror that come destroying portions of man, but the word used is 'angel'.
If you understand that the word 'alien' means, basically, "outsider", then the term could be applied to demons because demons come from the kingdom of darkness and try to get INto us. They are outsiders, foreigners that attempt to set up 'stakes' on the property of our bodies and minds. The have the ability to get IN to our bodies and manifest sickness and dis-ease; they can get into our minds and cause mental illness and all sorts of emotional disorders. They are alien because it is not God's will that they do that, but He will not violate our will and so allows them access when we sin or if we have generational curses in place in our lives.
Ironically, Hollywood has pretty good take on the demonic-ness of 'aliens'. They are always grotesque, usually larger than humans, and have supernatural (demonic) strength.
Per an Advanced Deliverance course I took, our government has the ability and technology to do everything you see in the moives...Everything. These technologies are in reserve for the End Times. The Gov. thinks they will use it to control the masses and kill them if they don't comply. But GOD has other plans for these things. They will be used of His good purposes which is to bring the masses into the Kingdom of Heaven.
Maggie