Safehold series

Hiding secret agendas from their subjects throughout a terrible war in the Charisian Empire, the Emperor and his inner circle of advisors launch a desperate counter-attack against a corrupt Church of God Awaiting that is complicated by a discovery in the Church's Zion Temple.

"For centuries, the world of Safehold, last redoubt of the human race, lay under the unchallenged rule of the Church of God Awaiting. The Church permitted nothing new--no new inventions, no new understandings of the world. What no one knew was that the Church was an elaborate fraud--a high-tech system established by a rebel faction of Safehold's founders, meant to keep humanity hidden from the powerful alien race that had destroyed old Earth. Then...

"When the leaders and soldiers of the tiny island of Charis rise up behind cybernetic avatar Merlin to defend their home, a powerful Church of God Awaiting, pushed to the brink of defeat, draws on its formidable resources and forbidden technologies in an ultimate battle between freedom and oppression." -- From Novelist.