Everyone hates random encounters! Or at least that’s the common wisdom. Random encounters derail the throughline of an adventure. They break the momentum. They force characters to use up valuable resources that’ll be needed later in the set-piece encounters still to come. In the worst-case scenario of characters being so tapped out of spells and limited-use features after a random encounter, everything grinds to a halt while the GM figures out how to work a long rest into what was supposed to be a time-sensitive adventure.
What’s the Story?
I go on about story in D&D (and by extension, all of its many offshoot games) from time to time, because I believe quite strongly that story is the foundation and end goal of all RPG play. So it should come as no surprise that I treat random encounters as just another part of the GM’s story-generation machine, by focusing not so much on the mechanics of what kind of encounter is called for and how tough that encounter should be, but on what kind of narrative the encounter can help build.
In keeping with the general bent of the game to define itself as being supported on three pillars of social interaction, exploration, and combat, those three facets of the game make a good starting point for thinking about how every random encounter might play out. But we can then add an additional layer to our random-encounter triad, thinking about random encounters as a means of delivering lore and exposition in a nicely dramatic package.
Social Interaction
As pretty much every version of D&D is quick to point out, not every monster is a monster. Which is to say, the world is filled with creatures who adventurers can meet, and those creatures can have motivations other than fighting, killing, or eating said adventurers. More interestingly, even some of the creatures who do want to fight, kill, and eat the heroes often have motivations that can tame those urges.
So how do characters find out what type of monster they’re dealing with? By talking, of course. A well-armed adventuring band is generally a daunting presence, giving a lot of monsters reasons to listen if the characters make an immediate offer of no hostilities. A group of wandering creatures with no real interest in what the characters are doing might simply agree that both parties should go their own way. The initial sense that combat feels imminent makes for a nice moment of tension, and a successful parlay to prevent that combat creates a sense of success that all the players can share in.
Lots of different kinds of social encounters can play out with a wandering band of intelligent creatures, from those creatures being lost and looking for directions, to creatures looking to trade equipment, magic, or information, to a protection racket where creatures more powerful than the characters ask for payment to let the party go. You can dial up the social aspect of that last encounter even more with some roleplaying or an increased payment, letting the characters convince the creatures to go ahead of them and clear out any other random encounters that might lie ahead.
Exploration
As has been said, the best offense is often a good defense, which makes avoiding a fight the ideal way to win it. Outside of a scenario where two groups confront each other coming around the corner of a dungeon corridor, you usually get to decide the distance at which a group of wandering monsters is seen. So by giving the characters enough lead time and a bit of initial cover, you can easily build any random encounter into an exploration mission dedicated to getting around or away from the imminent threat.
Exploration-based random encounters can be simple. Literally two minutes in game as you describe what the characters see coming toward them or following behind, and the players telling you what approach they take to staying unobserved while they go around the threat. But even the quickest and most seemingly uneventful avoid-the-monsters encounter helps flesh out the story, reminding the players and characters (and you) that the world is an active, dynamic place where things happen and the characters are going to stumble into those things from time to time.
Combat
All this talk about not making every random encounter into a combat encounter shouldn’t be taken to mean that random encounters should never be combat encounters. For most groups, combat is great fun. But you want to make sure that combat random encounters don’t start draining the characters’ resources in a way that’ll mess up the progress of the campaign.
First, focus on easy encounters that shouldn’t drain too many of the characters’ resources, whether that means combat with lower-threat foes or fights with more daunting foes who run as soon as they realize the characters aren’t going to fall as easily as first thought. And in the event that the characters do spend resources in a fight that you’d rather they didn’t, you can make sure a combat random encounter gives them a chance to replace some of those resources. If taking on debased cultists leaves one or more players with long-term conditions, give the cult leader a couple of spell scrolls of lesser restoration or greater restoration. If driving off a pack of dire wolves leaves the characters in a hit point deficit, maybe there’s a magical pool nearby that acts as a potion of healing once per week for any creature — and is what the wolves were protecting when they attacked the characters.
Lore and Exposition
Random encounters are often set up in a way that wants to detach them from the main narrative of an adventure. But beyond whatever fun you can have with them as you play, every random encounter can also serve to push specific bits of lore and exposition into the story — even lore and exposition you hadn’t thought about before.
Lore and exposition are often most closely associated with the social encounter pillar, but both can be worked into combat and exploration as well. Whenever the characters encounter other creatures, those creatures might have information they can reveal. A behir has heard a rumor and is willing to trade it for a favor. Avoiding a gnoll ranger patrol lets the characters see the gnolls use a secret trail leading to their hideout. A bandit chieftain who flees a fight drops a satchel full of maps that will give the party an edge as they seek a lost temple. Any time you have information ready to drop into an adventure, a random encounter can make a great time to do so.
But there’s another level of lore that random encounters let you play with, as you think about the encounter’s place in the adventure — letting the encounter becomes its own lore as you patch the appearance of monsters and other foes into the story. Roll up an orc war band during an adventure where the characters are going after evil stone giants? Guess what! You just determined that the giants are using orc mercenaries to patrol the territory around their lair, even if that wasn’t part of the adventure setup. Roll up a chuul in an environment where a chuul doesn’t make a lot of sense? There’s suddenly a portal to the Far Realm nearby that the players will never know you just made up on the spot.