When running a role playing game one of the major tasks for the game master is to bring encounters to the players. Here is my summary of the various methods I have used over the years.

Random

This is an improvised encounter method. The original and simplest of all methods, also very low prep. You create a method of choosing something to encounter at random and play out the interaction. There are lots of different ways of doing this but the old school procedure is as follows:

• Create a list of people or creatures that may be encountered.
• Assign each element in the list a dice value index.
• Set a dice roll mechanism for deciding if, at the end of any time interval, a selection should be made from the list.

Variations include encountering interesting terrain features, traps, changing the weather or triggering events that will impact on the play group.

As well as some “whole world, default list” you may have encounter lists that are used only when the players are in a specific region.

The lists may also contain more detail about the nature of the encounter, and for encounters with people and creatures there is also the random reaction table so you don’t always just assume hostile encounters. For example:

Roll d6. On a 1 or 2 -> hostile, on a 3 to 5 -> curious but neutral, on a 6 -> friendly.

These articles add some nuance here.

Breathing Life Into the Wandering Monster

Thinking About Wilderness Travel

Sample Method with encounters and weather events:

Random Encounter Mechanism v4

Keyed

This is a prepared encounter method. You have a map and for locations on the map you place an index key to a prepared location encounter. The amount of detail that is provided may vary, all the way to complete statistics for each person or creature, objects in the location, likely reactions, agendas and so on.

There is a lot of considerations into how you best record such information. Consider how important any piece of information is to your preparation for a next session. Be more inclined to prep information that will get a lot of re-use and that is more likely to be experienced by players sooner, rather than later.

The Art of the Key

There are some encounters that are implicit based on the location, e.g.  (bartender, shopkeeper, gate guard).

Ready Random

This is halfway between a prepared encounter method and an improvise method.

Prepare an extended encounter with details that can be dropped in at random to places in your world. For it to work it should have some external landing nodes that are adjusted to make the encounter fit the location where you decided to add it. These landing nodes foreshadow the encounter, also avoiding the Quantum Ogre problem (below).

Example.

The main node is a shallow cave with a pack of dire wolves in it. There are countless bones here, including some of unfortunate humans. The wolves are aggressive, especially right now as they have four new born cubs in the group.

The landing node is a stream down from the cave. There are wolf tracks here and a strong scent of wolf, and decayed carcasses, coming down from the cave. The stream is slightly screened from the cave mouth by bushes. There is a 1 in 6 chance during the evening and morning that a single dire wolf will be met here having a drink.

The Quantum Ogre

Ready Random can easily lead to the Quantum Ogre problem, that is you have an Ogre you want the players to encounter, no matter which way they go, or how much they try to avoid the Ogre, you plonk it right on them anyway. And not just ogres, it could also be a Tarrasque. The following articles explain the concept very well.

On How an Illusion Can Rob Your Game of Fun
On Slaying the Quantum Ogre
On Resurrecting the Quantum Ogre and Having Him Over for Tea
On the Corpse of the Quantum Ogre

Rostered

This makes a keyed encounter dynamic. You catalogue all the creatures changes of location during a routine day. Players encounter them in accordance with that roster until such time as the routine is disturbed.

The Art of the Key – Part 4: Adversary Rosters

Projected

This is an improvised extension of a keyed encounter projected out to locations beyond the key’s home base. The random encounter system needs a way to call on a “projection” encounter. You then scan the keyed encounters nearby to see if one might project into the current location, the creature being present, or some spoor of the creature, a rumour about it and so on.

Projected encounters are a type of “Wandering Monster”.

This procedure may be useful to you here and with Ready Random encounters

A Procedure for Wandering Monsters

Events

Encounters summoned, as mentioned earlier, may not be just monsters or people, they may include events, such as: fire, quake, eruption, flood, landslide, an accident, a brawl, a battle, a mob, a lynching, robbery, an explosion, an eclipse, a meteor shower, a hijacking etc.

Also weather events can breathe life into your game. The random encounter mechanism pdf above includes an example for handling weather alongside your normal encounters.

In this area you could also include encounters with “Patrons”, a feature of many games and wonderfully supported in Traveller through the 76 Patrons supplement.

Difficulty and Frequency

Looking at encounter difficulty and frequency is a more complex subject, especially since difficulty could mean much more than some combat adversary.

Revisiting Encounter Design

Connecting Encounters Together

Keyed encounters are most readily connected to each other, the link from one encounter to another can be prepared in advance. This is going to be easiest in a scenario that is node based.

Node-Based Scenario Design – Part 1: The Plotted Approach

However its not obvious how to get the same value out of a sandbox style game, or in an open table. However, it can be done, especially with Ready Random encounters. You can have linked ready encounters where one indicates the general area where another will be found. For example a clue in a ready random may point to the dark forest, indicating that a map is buried there. The map encounter, complete with trap and guardian, are free floating until players tread on the landing node by happen stance. They may have been given a description that allows them to know that what they seek lies beyond.

There are other ways to build a node network on the fly but its a bit involved and will have to wait for another day.

Conclusion

All these techniques and considerations represent a palette of useful tools for game masters to summon encounters as needed for player interaction and excitement. They blend improvisation and preparation to differing degrees giving you a lot of flexibility.