What is the key concept of the Great Commission: Roman Oppression card game

About The Great Commission: Roman Oppression Card Game, from BoardGameGeek:

The Great Commission: Roman Oppression is a stand-alone sequel and expansion to The Great Commission Strategic Card Game, with two exciting developments: A new competitive mode and more cards, mechanics and game modes for the original co-op/solo game! Set in the first century AD, the early church is established but still struggles with internal sin, conflict and spiritual issues. The Roman State, exerting severe political, economic, and religious oppression, is determined to honour Caesar. The bold contemporary artwork is drawn from the New Testament books of the Word for Word Bible Comic. -description from the designer