Quite well-known is the book of Revelation’s (aka John’s Apocalypse) condemnation of “worshiping the beast” in his writing to the Christians in Asia Minor:
[The beast rising from the sea] was given authority over every tribe and people and language and nation, and all the inhabitants of the earth will worship it, everyone whose name has not been written from the foundation of the world in the book of life of the Lamb that was slaughtered (13:7-8 [NRSV]).
Scholars have for a long time recognized in this a reference to worship of the Roman emperor, with the emperor being cast as a chaotic beast in this passage. In the Greek part of the empire (including Asia Minor), in particular, the emperor and the imperial family were granted honours equivalent to those offered traditional deities, like Zeus or Artemis. They were referred to as the “revered ones” (Sebastoi), the Greek equivalent of the title “Augusti”. This worship included temples in their honour as well as sacrifices at both the city and the provincial levels.
Yet quite often those who have studied these “imperial cults” tend to see them as primarily political and lacking in religiosity, or as “public” rather than “private”. This problematic view is partly due to the neglect of the many monuments and inscriptions set up by small, informal groups or associations at the local level in many cities of Asia Minor. Many of these groups worshiped the emperors without anyone imposing that on them. One such association at Pergamum was called the “hymn-singers” (hymnodoi). Once in a while they participated in special provincial celebrations in honour of god Augustus and his heirs, but they also engaged in special “mysteries” that lasted three days in honour of the “revered ones” within their local meetings. Similarly, an association at Ephesus in the time of emperor Domitian had “mysteries and sacrifices” which they performed each year “to Demeter…and to the Sebastoi gods”.
If you want to read more about John’s Apocalypse in relation to imperial cults, go here. If you want to read more about the associations specifically and their imperial mysteries, go here. For a short overview of the types of imperial cults, go here.