New Defender's Study Bible Notes
2:13 Satan’s seat. “Satan’s seat” is literally “Satan’s throne.” This may be a reference to the great altar of Zeus at Pergamos, but there is also some evidence that the priesthood of Babylonian idolatry had moved to Pergamos when Babylon fell to the Persians.
2:13 Antipas. “Antipas” means “against all.” Although Antipas may have been an otherwise unknown martyr (i.e., “witness”) at Pergamos, the Lord may have included his name here to represent all His faithful witnesses who take a clear stand for Christ “against all” the forces of Satan, even at the possible cost of martyrdom.