I wish you well in your efforts to keep your in-game use of magic on the down-low. I believe that it might not be possible to complete the game without your player character using some of the soul-based powers. You might be able to avoid taking spell casters with you, but based upon what I've read about Project: Eternity, I think your character will be passively and actively drawing upon the powers of their soul on a regular basis. If this smacks of the occult to you, then Project: Eternity might not be a prudent investment.
Have you taken your final vows to your order? If not, perhaps a pause to reconsider might be worthwhile. If a simple roleplaying game has the potential to put you in conflict with your more stodgy superiors, then I'd give careful consideration as to whether or not I'd want such people as my superiors. Meditate upon that and draw your own conclusions.