Pergamos (Pergamon) was a city in Asia Minor situated by the river Caicus. It was formerly the seat of the kings of Attalia and the capital of the Kingdom of Pergamon during the Hellenistic period (281 to 133 BC.). In 133 B.C. the city was bequeathed by Attalus, the last Attalia king, to the Romans in order to prevent a civil war.
The city library, which contained two hundred thousand volumes, is considered the second best library in ancient Greek civilization. The library's fame was such that Mark Antony gave it to Cleopatra as a wedding present. The city was also known for creating, out of fine calfskin, a replacement for papyrus. The replacement was called pergaminus or pergamena (parchment) in honor of the city.
The Great Altar of Pergamon, built in the first half of the second century B.C., is currently housed in Berlin's Pergamon Museum. The base of the altar depicts a battle between giants and Olympian gods. The altar's frieze prominently displays a likeness of Zeus. In Greek mythology Zeus was considered the father of gods and men who ruled the Olympians of Mount Olympus. The Greeks believed Zeus was the KING of the gods who ruled the entire universe. It is possible that Pergamon's monumental pagan altar was being referred to when God told the church in the city that he knew they lived "where Satan's throne is." (Revelation 2:13).
Pergamos is the third of 7 churches of Revelation given an overall evaluation directly by God:
"These things says He who has the sharp two-edged sword:
"I know your works, and where you dwell, WHERE SATAN'S THRONE IS. And you hold fast to My name, and did not deny My faith even in the days in which Antipas was My faithful martyr, who was killed among you, where Satan dwells.
"But I have a few things against you, because you have there those who hold the doctrine of Balaam, who taught Balak to put a stumbling block before the children of Israel, to eat things sacrificed to idols, and to commit sexual immorality. Thus you also have those who hold the doctrine of the Nicolaitans, which thing I hate. Repent, or else I will come to you quickly and will fight against them with the sword of My mouth.
"He who has an ear, let him hear what the Spirit says to the churches. To him who overcomes I will give some of the hidden manna to eat. And I will give him a white stone, and on the stone a new name written which no one knows except him who receives it." (Revelation 2:12-17, NKJV, emphasis added).
Balaam was a prophet who was asked by Balak, the king of the Moabites, to curse Israel as they camped in the wilderness. God warned Balaam not to curse his people by miraculously having a horse talk to him and the Angel of the Lord appear ready to kill him (Numbers 22-23). The prophet's way around not being able to curse the Israelites was to teach Balak how he could lead Israel to corrupt itself and thereby bring God's judgment down upon them (Numbers 31).
The Nicolaitan doctrine was one which promoted a rigid top-down governmental structure in the church. Such a hierarchy, where some who feel superior (elders or the ministry) dominate and rule over the faith of others (the laity or brethren), is opposite that of God being the only master and Lord of all.