[See Seven Churches]
Pergamum is a region in Asia Minor, currently part of Turkey.
It was a very prosperous city at the time, with numerous temples to foreign gods, and the temple of Zeus, in particular, was famous for its immense size.
As a place with many pagan temples, it was a site of intense spiritual warfare, and it is here that the Lord appears with a sharp, two-edged sword.
Rev 1:11saying, “Write what you see in a scroll and send it to the seven churches: to Ephesus, to Smyrna, to Pergamum, to Thyatira, to Sardis, to Philadelphia, and to Laodicea.”
Antipas, of the early church, was martyred here. The "throne of Satan" mentioned here also seems to refer to the situation of this city with its many pagan temples.
Rev 2:12“And to the angel of the church in Pergamum write: ‘The words of him who has the sharp two-edged sword.Rev 2:13“‘I know where you dwell, where Satan’s throne is. Yet you hold fast my name, and you did not deny my faith even in the days of Antipas my faithful witness, who was killed among you, where Satan dwells.Rev 2:14But I have a few things against you: you have some there who hold the teaching of Balaam, who taught Balak to put a stumbling block before the sons of Israel, so that they might eat food sacrificed to idols and practice sexual immorality.Rev 2:15So also you have some who hold the teaching of the Nicolaitans.Rev 2:16Therefore repent. If not, I will come to you soon and make war against them with the sword of my mouth.Rev 2:17He who has an ear, let him hear what the Spirit says to the churches. To the one who conquers I will give some of the hidden manna, and I will give him a white stone, with a new name written on the stone that no one knows except the one who receives it.’