"The OSR" is like a tiny parasol held aloft by an elephant. It's too small of an umbrella to do any good.
However, it's all I have to work with right now!
What I consider an "OSR encounter" is one that challenges the player's imagination, creativity, role-playing, and critical thinking skills. The less it has to do with rules in the books and rolls on the table, the more "OSR" I consider the encounter.
As a B/X player, that's what I'm seeking when the GM introduces an encounter. Yes, sprinkle a few pitched battles in there sparingly, but in a game that's billed as OSR, I don't want to roll a d20 back and forth for an hour of play, let alone two, maybe even three. It's usually boring if not tedious, but it can be grueling when the dice are disagreeable.
Yes, we want to kill monsters and take their stuff by attacking in combat. Yes, we want to explore a maze of corridors using the procedures detailed in the books. However, if that's all we wanted to do, we would be better served by a more robust rules set such as AD&D or a later edition.
Let's examine a common example of a dungeon encounter that can be fun, but I don't want to dominate my time at the table:
There is a platoon of six goblins with shields and spears at the edge of your torchlight in this 10'-wide hall. One shouts, "Death to the day-dwellers!" and readies his javelin.
A little "fluff" combat, especially in a level 1 starter adventure, is okay—but just throwing dice at the bad guys until their hit points run out is an insipid grind, especially for the initiated OSR player. Rolling dice can be fun, but isn't intellectually challenging, and that's something I want in a table-top fantasy role-playing game.
Basically, designing an "OSR encounter" is an exercise in making it not just combat.
Perhaps the most well known example of an OSR encounter is "There's a moat with crocodiles. How do you cross?" Yes, you can fight the crocs, but it can be more fun to come up with all the different ways to get over the moat other than "I hit them with my sword."
Part of the fun in the OSR is in thinking of things like, "I hunt for wild boars in the woods to use as bait to lure the crocs out of our way."
In Stonehell Dungeon, one of the first "patrol of humanoids" encountered is a handful of kobolds. They're a great, memorable OSR encounter.
They have mining equipment like pickaxes and hammers. They have no intensions of attacking the players—they just want to pass. Simple as that.
Sure, the players can attack and kill them all. Or, they can devise countless other ways to have a great deal more fun with them. For example, at the price of a few measly trail rations, they make good guides. Only a fool would make enemies when they could make allies!
As another example—only half as a joke—this one is a great OSR encounter from The Caverns of Steel:
"Three steel crustaceans challenge the party to a dance off, by pointing at them with a claw and then doing a little dance. If you win, you get a loyal metal-crab follower."
It's too silly for my table. I'd never actually use it, but it's great example because it shows how a good OSR encounter relies entirely on the player's imagination, wits, and strength at role playing.
A bad GM will screw this up by making it a contest of CHA rolls or whatever. Ouch. That's the exact opposite of what I seek in an OSR encounter.
For B/X players, the OSR is "rulings not rules." We "play worlds not rules," and, "The answer isn't on the character sheet." It's a test of the players' skills and creativity, not of their characters.
