This sermon looks at the way the church of Pergamos had penetrated the heart of Satan's kingdom, what it meant that Satan's throne was there, and the lessons (positive and negative) from how Pergamos handled that.
Jesus rebuked the church of Thyatira for tolerating the spirit of Jezebel in their midst. What is this spirit of Jezebel? Dr. Kayser walks through 15 of the Old Testament characteristics of the demonic stronghold symbolized by the name "Jezebel" (and displayed in the woman herself), and explains how this otherwise solid church could have tolerated a Jezebel for so long.
The previous sermon explained the problem of the Jezebel spirit; this sermon explains the solution. Jesus Himself _is_ equipped and motivated to deal with Jezebels and Ahabs, and through His authority and power, we can be equipped to be Elijahs rather than Ahabs.
The central problem with Sardis was a satisfaction with a form of godliness even when the power was gone.