The regulation of violence in a setting helps to characterize the PCs and their place in the world. When they act wantonly, they might be treated as a wanton outlaw. This is an interesting trade-off if there is some other social role they could aspire to, as trusted and respectable agents of an authority or friends to some kind of society. When PCs feel bound by social customs about violence, it presents all sorts of problems requiring creativity:
- How do we transport this captive back to the lord' palace?
- How do we draw our foe away from sanctified grounds so the gods will not protect them?
- Since we believe this promise from a foe at our mercy, do we accept their promise to take us to their buried loot?
- How do we arrange the death of someone we absolutely cannot kill?
Obviously, if you want to establish a cultural code around violence, NPCs need to cleave to it more often than not. If you want a setting where honor and reputation are important, you need to get in the mindset of not-quite-lies and working around the tenets of that setting. This models appropriate rules-lawyering for players. It also helps to have potential enemies respond to strangers in less immediately-homicial manners, showcased with something like False Machine's Ghibli-esque Monster Reaction Roll.
(I like to do a single, simple roll for reactions and morale. Something like:
D6 Reaction Roll
- Aggressive. If outmatched, will scatter if possible.
- Hunting. Hostile, but won't start an outright fight. If attacked, will give a fighting retreat.
- Mixed. Upset, incensed, or worried. If a group, some are aggressive.
- Flighty. Will retreat at first sign of trouble.
- Curious. Inquisitive, but ready to fight. If attacked, will give a fighting retreat.
- Friendly. If outmatched, will scatter if possible.)
In a land of surrenders, yields, and promises, a foe might not even take someone captive if they swear an oath to leave and not come back. If you really fear someone's revenge, you can always just cut off their sword hand (only for that to be avenged a few sessions later.) I'm just saying, there's a range of outcomes for characters to negotiate, and this ties PCs to the world through the actions they observe in NPCs, in the reputation they have to consider, and ultimately in the feeling of obligation their characters may come to develop, even when no one is watching.
Part of why I enjoy rolling for death and dismembering after reaching 0 HP is that it delineates a point for duels "to the yield." It also means there's one roll on the dismemberment table, which keeps risk present.