Luke 22:1-71 (New King James Version of the Bible)
Now the Feast of Unleavened Bread drew near, which is called Passover.  And the chief priests and the scribes sought how they might kill Him, for they feared the people.  Then Satan entered Judas, surnamed Iscariot, who was numbered among the twelve.

Satan was there at the beginning of the Last Supper

In entering Judas, Satan entered someone who was one of the twelve, the closest group of people to Jesus.  One could surmise that Judas may not have truly submitted to the Lordship of Jesus, but Jesus once rebuked Peter with the words "get behind me, Satan!"  Peter was a true disciple.  Can someone who is a true follower of Jesus be influenced by demons without being "oppressed"?  How easy is it for Satan or one of his demons to put a thought into my head? 

Furthermore, Satan did not simply make suggestions and thereby tempt Judas, he entered him. That seems far more powerful and intimate.  It implies control, perhaps, or at least great influence.  Since Satan is an archangel, can angels enter people and act through them?  Maybe they can, but choose not to do so and leave that up to the Holy Spirit, who resides in people who follow Jesus.  Still, it is startling to consider how close Satan was to an event so sacred and that he was allowed to enter someone who was among His closest disciples.  He probably looked just as righteous as the rest, at least on the surface.  I wonder, who are the people most influenced by evil in my community, and how respectable do they appear on the surface?