SHARK said:
What now? What do you think? I was amazed that she granted her mercy! Just incredible! A priestess of Orcus no less!
Consider very carefully on how things will unfold from here. This has amazing story potential for good or ill. It harkens back to the attempt by Frodo to redeem Gollum. Just be careful - if the priestess strikes out at the players without cause, they would be well justified indeed in never showing mercy again.
Indeed, this is the type of players Ravlek deserves - automatons who kill anything that sets off the detect evil alarm without any cause, because the rules say so. I have a feeling though that that isn't the type of game your running SHARK.
If you don't already have it, I'd recommend a look at the Book of Enlightened deeds. It has quite a bit of advice on this situation, on the things can go right, and go wrong.
Redemption is a powerful thing. Yes, Orcus will turn away from the priestess, and former allies will become enemies to her, but other gods need followers and in time perhaps one of them may grant spells to her.
Mercy, compassion and the chance for redemption are as uniquely good as treachery, grudges and hatred are evil. This paladin is taking a huge gamble with his life and the lives of his friends in offering mercy and trying to redeem this priest. Understand that if you punish this as Ravlek recommends, your players may never do this again - and they will be justified.
Ravlek, you are so wrong on so many levels it isn't funny. Mercy, compassion, forgiveness and redemption are part of good's identity. A refusal to offer mercy to a foe who has surrendered is an evil act - not the reverse as you so strongly argue. If this priestess betrays the trust she's been given it is her for it - it is no sin on the paladin. While the paladin has every right to be mistrusting of this priestess, if there is even the tiniest hope of redemption for her then he is obliged to try - not turn away as you argue he should.
Stories of redemption are some of the most powerful and moving in literature.
Return of the Jedi anyone?
Oh, and BTW, the rules you're quoting don't even apply anyway. Followers & cohorts are the NPC's gained through the leadership - and this priestess is neither of those - she's an incidental character that may or may not remain with the party: at the moment it's unclear what will happen. If she is to remain she must of course redeem herself - but that's a long term judgement, not an overnight one.
Or are you going to argue that if an evil PC joins the party the paladin instantly loses his paladinhood?