Wow, Xan! Now we're talking! I have similar fantasies (not lately though - I had to think back a bit to really get at them, had thought of them yesterday though). To me they're linked with Roger Dean's cover art for bands like Yes and Uriah Heep in the 1970s. Dean once described a cover painting he prepared but never fulfilled for Relayer (1974) - a Yes fave album of mine - as showing "a huge cave-like crypt, a cathedral for a warrior order, with hundreds of military monks celebrating mass". This is your setting, right?
I totally agree about this idea of being brought in bound, thronged by men and chained and fucked on the altar stone. This rough-hewn, angular setting and vaguely pagan, warrior-cult am_bie_ce gives the place its own flavour.