I like them. I like Classic Traveller, which defines a structure for these tables I have to fill in. But I am missing a structure or recipe for creating tables in other systems.
So how do you create random encounter tables?
How do you handle different themes?
How do you handle challenge ratings?
How do you decide on likelihood?
Do you include modifiers for circumstances?
What else do you address when creating encounter tables?
(Please don't just post "I don't do encounter tables." I am looking for recipes and not for your opinion on encounter tables.)
I guess I am probably just a creature of habit from old school RPG/D&D.
Encounter tables (for me) start with the "terrain" - is it urban, rural, wilderness.
Next, why would the players BE there - what's the "hook" that triggers the encounter from the player view?
Then, brainstorm all the things they can run into: traps, ruins, the ecology of the creatures that live there, the people who might have settled, others passing through from some reason, etc. You just make a list - or even better - scan through previously made lists (yours and others).
Now weed out the list of ideas that you *don't want* to run as an encounter in the next few sessions.
If something is "close" but "not quite right" can it be reskinned to fit this circumstance?
Finally, you pick probabilities - this can be the easiest: just treat the "random" encounter table as a scratch off list and use each item you brainstormed once, in order.
The only time "probability" of encounter really matters is when you're simulating an ecology... or a table of the random encounters you might have with creatures just doing their normal business of living in an area.
Then you think of it as "likelihood that a party will encounter the thing each hour, or day, whatever time unit... while they are in the area"
Then you can throw a dart at a dartboard and use the number as a "1 in #" chance each day of encounter.
The specific numbers don't really matter unless you're trying to realsitically simulate some existing thing.
So, here's kind of a thinking out loud example of the noise above:
Where are the players? Terrain: Wilderness (jungle, space, underground, what have you)
Why are the players there? Moving through hex to get to ... - camping - scouting for food as they move
What could happen?
Animal attacks - bears, bulettes, wasps, dragons, what have you - what *lives* here?
Natural weather hazard - a storm turns the turf into muddy mess
Terrain hazard - broken rocky ground that slows them down
Wandering NPCs - hunters, criminals, settlers, other adventurers, madmen on vision quest, wizard gathering spell components, woodcutter, fur trapper
So, which if those encounters don't fit your upcoming session plan - cross them off for now, but save the ideas for later reuse
Now you have a list of ... possibilities.
Which need probabilities?
The weather and the animals.
For those, you break up days into hours-long blocks - morning, afternoon, evening, night.
What are players doing in those?
Morning - breakfast, pray/learn spells, tend animals, break camp, move on
Afternoon - stop, lunch and tend animals, break camp, move on
Evening - stop, tend animals, set camp, dinner
Night - set watch - rest
Each block might have a weather check and an animal encounter check if you want random surprise.
My guesswork starting point is basically choose a 1 in X value - where X is the number of the days the party would be crossing wilderness hexes
10 days trip - start each idea for an encounter with a 1 in 10 - and try to make the table have 10 different interesting ideas for that.
Day 1 - morning - rabbits at dawn - nice breakfast idea...
Day 4 - night - curious hungry bear
etc.
So, I just made all that up off the top of my head for this reply without cracking a book or diving into notes - maybe 10-15 minutes tops?
All of the old D&D and AD&D books have random encounter tables by terrain that are wildly reusable / expandable.