Having hastily perused Basic Fantasy Role-Playing Game Rulebook, I remember the Reaction roll, something that I've so quickly forgotten from my 3E and 4E days.
The reaction roll is for monsters that aren't predisposed to attacking the player characters. And with a random component to how each encounter begins then most play-throughs of an adventure will be significantly different. Interesting.
This is very analogous to random encounter tables, but instead of provides a mechanism for the GM to defer a decision regarding monster reactions.
Remember Vincent's Admonition? (TL;DR – “Roll Dice or Say Yes.") The admonition is for a GM responding to a player. But sometimes, a GM, without input from players, may not know what to do next. Enter the random encounter, reaction roll, etc.
So I am realizing there is a corollary for this admonition for the GM – “Don't know what to say or do next? Roll the dice.” I suppose that is what is behind the Mythic Game Master Emulator (a fantastic product in its own right).
Reaction Roll Table
Now back to the Reaction Roll Table from Basic Fantasy Role-Playing Game Rulebook.
Begin OPEN GAME CONTENT
|2 or less||Immediate Attack||The monsters are so offended that they attack immediately.|
|3-7||Unfavorable||The monsters do not like the player characters, and will attack if they may reasonably do so.|
|8-11||Favorable||The monsters will consider letting the player characters live if they choose to parley; it does not necessarily mean that the monsters like the player characters.|
|12 or more||Very favorable||The monsters (or perhaps only the monster leader) do, in fact, like the player characters; this does not mean that the monsters will just hand over their treasure, but it does indicate that they may choose to cooperate with the player characters in mutually beneficial ways.|
These days, when I see 2d6+n I think And when I see 2d6+X, I think its time for a move in Dungeon World. Given that the Charisma modifiers in Basic Fantasy RPG range from -3 to +3, this table could map directly, but would break with the concentric game design.
Dungeon World Move
When you attempt to placate one or more monsters that are waiting for you to make the first move, roll+CHA. On a 10+ they will cooperate with you so long as its mutually beneficial. On a 7-9 they are willing to listen.