This is a great text...
Luke 10:17-19 King James Version (KJV)
17 And the seventy returned again with joy, saying, Lord, even the devils are subject unto us through thy name.
18 And he said unto them, I beheld Satan as lightning fall from heaven.
19 Behold, I give unto you power to tread on serpents and scorpions, and over all the power of the enemy: and nothing shall by any means hurt you.
I believe we can stay right within the text and understand it perfectly. We don't need a smoke screen of Bible texts from all over the Bible to redefine what is being said here. There is no need for breaking out the secrete decoder Bible verses companion. lol
It's a rather simple conversation. Put yourself there with me in your mind's eye. Let's look at it and see what is actually taking place.
Here, the seventy return rejoicing that even the devils are subject to their authority through Christ's name. Jesus makes a statement much like the "Before Abraham was, I am.", statement. Jesus says, "I beheld Satan as lightning fall from heaven." This implies that Jesus pre-existed as God. Now, why did Jesus harken back to a time perhaps prior to the creation, telling the seventy that He saw Satan fall from heaven? Jesus was clearly stating that He was indeed present when Satan fell from heaven, and implies that it was He (Jesus) who had cast Satan out of Heaven. This statement is intended to affirm Christ being God and build, and expand, the excited faith of the seventy. They had authority over devils through His name, because He (Jesus) was the one who cast Satan out of Heaven to begin with. Jesus then explains that He will now give them power and authority to tread on serpents and scorpions (symbolic of demons and demonic devices), and promises divine protection.
Also, the linguistic structure of the text indicates that Jesus is speaking about an individual being, not a group of demons, the mayor of Jerusalem, or a broad philosophic non-personal concept.