Bear with me for some foolishness - a thought experiment. How might PCs respond to cycles of time treated as sacred by society, in ways that evoke real Medieval Europe more than the Modern/Wild-West-American-frontier-with-knights-vs-hobgoblins pastiche that D&D often ends up presenting, whether consciously or otherwise?
[EDIT: I had only just drafted this post this morning and left it to stew for a bit, and then later in the day saw that B/X Blackrazor's post today explores some very similar stuff. We're talking about completely different subjects, but both posts raise the issue of character alignment in light of pre-modern cultural sensibilities. Worth a read in tandem, if this interests you.]
THE "PEACE OF GOD"
Let's start with the "Peace of God/Truce of God" movements that grew up across western Europe (primarily France) during the central Middle Ages, especially during the 11th century. In a nutshell, the late Carolingian empire had fragmented, feudal society was becoming particularly chaotic, violent, and unruly, and various social groups (centered around the church but also reflecting popular initiatives) started pushing for controls on the violence tearing apart what was supposed to be a unified Christian society. This process led to things like local militias supported by "clerics" cracking down on feuding nobles; voluntary oaths by which aristocratic warriors pledged to restrain their intra-Christian killing; and calendrical restrictions, whereby fighting was prohibited from Thursday through Sunday, and only allowed Monday-Wednesday. These comments only scrape the tippy-tip of the iceberg; Pax Dei scholar Richard Landes offers a deep dive here if you're interested. A key point I want to stress is that the Peace of God aimed, at least, not only to reduce violent incidents, but to introduce multiple days-per-week as a kind of Sabbath from violence, the institution of a millenarian 'peaceable kingdom' through the manipulation of social time, reinforced by social peer pressure or even (when necessary) by the 'legitimate' violence of popular militias.
[AN IMPORTANT CAVEAT: these movements also ended up contributing to genuine awfulness, as violent people agreed to less killing of Christians and then transferred those energies onto non-Christian populations - leading both to pogroms and crusades. To be explicitly clear, I am neither endorsing nor equivocating about such horrors, nor am I calling for their inclusion at the gaming table. I mean only to ponder the game-effects of ritual constraints on violence for groups like NPC-fighting PCs. In fact, this idea only has gaming utility to the extent the PCs' society recognizes the innate value of NPC lives].
SACRED TIME AT THE GAMES TABLE
So you've got a sandbox setting chock full of those 'points of light' surrounded by villains and brigands in a chaotic wilderness (this works best, of course, if humans/humanoids with valuable lives have a key role as potential antagonists). Ponder seriously for a moment a social response that severely restricts WHEN "good guys" are supposed to draw swords and have at their enemies. Implementing some kind of ritual, social regulation of violence in a fantasy setting could have nuanced effects on gameplay. Let me elaborate.
+ If the PCs are the kind of people who are expected to honor "days off" from fighting for the good of society, this would introduce an interesting periodicity to campaign play. Well, I suppose this could become a boring periodicity, but if handled well it would interweave opportunities for exploration, intrigue, diplomacy, and other non-violent options (not to mention 'domain management' in general) among high-intensity days suited for bashing enemy heads. It also would force multi-tasking and creative problem-solving - or require players to accept the consequences; all good OSR principles.
+ Ponder cycles of sacred time in a campaign setting. At most RPG tables, I suspect, DMs and players alike think of TIME in wholly modern ways. Gary Gygax had his famous dictum about how essential proper time-tracking is; for most RPG heroes or knaves, we may play at roles we think evoke the "days of yore," but we (and by extension our characters) consider time a neutral, impersonal commodity entirely at our disposal in a game of 'resource management' - an attitude grounded in our modern Western context and very, very alien from many pre-modern settings (not the least, Medieval Europe). If we are content that way, then great - but what might it do to start inhabiting a more pre-modern view of time through our role-playing, a view in which time is ordered and highly ritual-bound, not a commodity purely at our disposal but a sacred process into which we are invited; something with its own rules and patterns and proper seasons that we can ignore only at our peril, and which we can follow to find our proper place in a 'timeless' scheme of things...
|Pettie, The Vigil (Public Domain)|
It would be a different psychological experience, I think, to play characters capable of as much murderhobo-ing as any group, but who regularly face social/cultural constraints that demand that the characters fit into the setting rather than always remaking the setting in their own image. I'm not talking about railroading player choice, but presenting clear, setting-appropriate constraints within which player choice can operate. By using constraints of time to influence PC behavior, one still allows the shenanigans typical of RPG 'heroes,' but forces players to think critically about those behaviors and adapt them to social or even supernatural responses. Imagine how these would affect a campaign:
+ canon law clearly states that dungeon-crawling is acceptable any day of the week, but fighting humanoids is off-limits on weekends. Deep within a dungeon, PCs suddenly face a moral-practical dilemma - clear out these Duergar, or risk that old rope-bridge to go around them for now and come back if needed? Of course, violating the Peace has its own risk, because...
+ Imagine that paladins lose their powers if they break the Peace by fighting on the wrong day. Clerics lose access to offensive powers on specific days of the week (but perhaps they can use those powers more frequently than usual on the 'ok days'). More extremely, Peace-breakers are supernaturally branded, visibly marked as agents of Chaos.
+ Beyond such supernatural measures (or responding to them), social consequences abound. Those known as Peace-breakers are ostracized or even hunted by the forces of law and order, but also sought after by highly unsavory types. Much as "alignment languages" once offered a (rather weird) social collective for alignments, the basic question of alignment/non-alignment with the Peace becomes a defining factor for PCs' social relations. This leads to many further dilemmas. Does self-defense violate the Peace? If not, can canny PCs provoke a villain to attack them at the wrong time? If the enemy base absolutely, positively must be infiltrated today, are PCs willing to accept the long-term consequences of branding themselves as Peace-breakers to provide 'undercover' legitimacy that gets them inside the base? On and on.
As something of a sweeping generalization, pre-modern Mediterranean and European religious life tended to emphasize practice over intellectual belief (much more so for the ancient period, but even much of Medieval Europe looks this way compared to modern society). This principle offers food for thought about alignment systems; in a practice-oriented society attuned to questions of honor and shame, what are the social consequences of Lawful or Chaotic behavior? How do social expectations fundamentally constrain the types of actions - or at least the timing of actions - that PCs can get away with?
Anyway. Thought experiment.