e1ven said:
But I don't want this to be the only action on the table. If they're making a choice to do this, instead of something else, I want them to know the other options that they're not taking.
It sounds like (A) you are using alignment and (B) these particular slavers abuse their slaves. That suggests that at least those involved with the abuse are Evil. The D&D alignment system says that "Good characters and creatures protect innocent life." and does not say that Good characters are pacifists who cannot kill (though certain deities could certainly be pacifists). Clearly, at least some of these slavers aren't innocent and those involved in the cruel abuse of slaves should be Evil in alignment.
If the PCs have the ability to detect alignment, it should be possible to seperate the guilty (Evil) from those who are simply going along as part of their job (Neutral) without waking anyone up. I would argue that if the PCs don't take that extra effort to seperate the guilty from the innocent (i.e., "Good characters and creatures protect innocent life." and "Good characters make personal sacrifices to help others."), then they are being Neutral or even Evil, not Good. On the other hand, if they only single out the Evil for retribution, their actions would be Neutral or even Good, and not Evil, in my opinion.
e1ven said:
Mallus, I agree with you, in practice. I just want to make sure they know they have options, so this is a dramatic choice, rather than them feeling railroaded into doing something evil.
I don't think that killing the slavers is Evil if the objectives are (A) to free the other slaves, (B) to make sure they don't buy and abuse slaves in the future, and (C) the slavers being killed are Evil and guilty of abusing slaves. I'd argue that it's only Evil if they don't make an effort to differentiate the alignment of who they are killing or go out of their way to be cruel to those they kill (the whole revenge as a path to the Dark Side thing). Nothing about Good says that you need to wake Evil up, put a weapon in its hand, and let it defend itself.
e1ven said:
They want other options. They've been praying to their gods for them. I'm just looking for what to give them
The (now ex-)paladin in the game that I'm running was confronted with an injustice that he wanted to go off and fix that was Evil but relatively minor in the big scheme of things. I had his patron saint give him a vision (three versions of the same vision, actually, as time went on).
The first version involved a lone traveller on a road outside of a city being ambushed by cut-throat bandits. As he watched, his patron saint rode up to the scene--and kept going. As he looked up, his patron saint was tracking a dragon descending upon the city and rode past the cut-throats with his eye on that dragon, which he took down with a single (symbolic arrow). In the meantime, the cut-throats killed the lone traveller and robbed him, leaving the body on the side of the road. The patron saint came back and told him, with a tear in his eye, "No, it never gets any easier."
The second version involved the woman he fell in love with and married. As before, the patron saint rode by and he watched as the cut-throats descended upon her, abused her badly, slit her throat, and left her in the mud to die. The patron saint came back and asked if the paladin could make the same choice. He knew he couldn't, which is when he ceased being a paladin. That was all the player's call.
The third version, the paladin was cast in the role of the warrior saint and was given the choice. Having thought it through and come to terms with his priorities, he left his wife to die to save the city, understanding as before that it's not an easy choice and never will be. The now-liberator (long story) realized that he also couldn't live with himself if he sacrificed thousands to save his wife.
Basically, have their deities paint their choice for them, not only in the short term but also over the long term. Illustrate for them, in their dreams if their deities favor them, what the moral and long-term implications of their actions might be. Do you want to run a game about ending slavery in the realm? If not, what greater purposes lay ahead for the PCs? If they have a greater destiny to live out and slaughtering all of the slavers will distract them from that destiny, then paint out their choice in those terms.
Basically, if slavery is the greatest Evil in your setting, then it makes sense for the PCs to confront it. Don't stop them. If it's not the greatest Evil in the setting and their deities have greater things planned for them, then paint their choice in terms of lesser and greater Evils and make them pick a right to wrong on those terms.