The Eye of Venus

This book, 'The Eye of Venus', is Book One of a trilogy. The other books are entitled 'Twenty Years On' and 'The Return to Chiaros'. This series, set hundreds of years ahead from now, and on another planet, is what I call (soft) Sci-Fi/Fantasy. Science and history are background to the story.
The story is of a quest for an emerald, a special emerald. The emerald is part of a device that was used for inter-realm passage.
The main competitors are Satanic forces, and a secret Catholic Church organization known as Probono Dei.