Planned Encounters (DMG)

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A planned encounter is one of the DM has prepared in advance, one tied to a specific place, event, or condition. These can be divided into keys and triggers.
==Keys==
The simplest of planned encounters is called a key—a listing of who lives where, what they have, and what they might do if a character enters their room, visits their farm, or explores their cave. This key can also contain colorful details about otherwise boring or empty rooms, creating detail for the player characters to explore. Here's how a sample key for an ogre's den, a three-chambered cave, might be written.
1. Main Chamber: One passage of this chamber leads to the outside, a narrow cleft in the rock hidden behind some bushes. Following this, the passage widens after 10 feet. The walls are coated with soot and there is a large pit in the center of the floor filled with ashes and charred bits of bone. The ashes are warm and the rocks of the pit are still hot to the touch. The chamber stinks of burned meat and leather. There is a lot of rubbish on the floor but there is nothing of value here. At the far end, the cleft once again narrows to a passage.
2. Sleeping Chamber: Here the air is thick with smells of animal sweat and worse. There is a loud rumbling from the far side of the chamber. There, sleeping under a mound of crudely skinned furs, is a large ogre. Next to him is a large wooden club. Hanging from the walls are bits of bright cloth, shiny buckles, and tarnished badges. A few simple torches, now unlit, are wedged in the cracks.
If the characters don't move slowly in this room, one will kick a metal helmet across the floor, waking the ogre. Groggy for one round, he then attacks the group. Just beyond the nest is another passage.
3. Treasure Room: The entrance to this chamber is blocked by a large boulder that must be rolled into the room to get it out of the way. Characters must get it out of the way. Characters must roll a successful bend bar/lift gates check to move it. (Several characters can work together, totaling their chances into a single roll.) Inside the room are the treasures of the ogre. These include 500 gp, 3 gems (worth 10, 500, and 100 gp), a suit of chain mail +1 the beast cannot use, and a mound of horse trappings, bridles, and saddles. Aside from the bats, there are no creatures in the chamber.
When you write a key, describe the way the scene looks as accurately as possible. Also think what sounds the player characters might hear, what they'd smell, what the place feels like, and so on. Writing a good key is like writing a good story. At the very least, include the following information for every location:
* Any monsters or NPCs found there.
* What equipment and magical items the monsters will use.
* Any treasure (and its location).
* Any other unusual items of interest. This can include colorful details to help you describe the area or clues to warn characters of danger ahead.
The key can also include special conditions that must be met while in the area. In the example above, there were penalties for not being alert and cautious (kicking the helmet) and requirements for Strength (moving the boulder).
However, keys are static—things don't change that much. No matter whether the characters enter at noon or midnight, the ogre will be sleeping. He won't be cooking his dinner, out hunting, or picking his teeth with his toes.
For fairly simple scenes this is fine, but the situation gets ridiculous for more complicated situations. Imagine a farm where the farmer was always in the field or a castle where dinner was continually being served!
Static also means that events in one place don't affect things in another. If the characters heave the boulder out of the way, won't the noise awaken the ogre? Not according to the description as it is given, although a good DM would certainly consider the possibility. Writing a key that takes all these potential inconsistencies into account isn't easy. To be complete, you would have to design the key in your head, figuring out all the interconnections, before you wrote anything down.
There are two solutions to this problem: You can try to be complete and thorough, preparing answers for every possible situation, or you can reduce the amount of detail you give about creature behaviors and improvise answers as you play. To describe a farmhouse, you could simply note the occupants (their ages and the like) and the significant possessions at the farm. The activity of the NPCs can be adjusted to the moment—working in fields, sleeping, eating, etc.
Trying to pre-plan for every eventuality is time-consuming—there is a fair amount of planning and writing you must do. Improvising cuts down on preparation, but forces you to work harder during the game. The best solution is to compromise: Carefully detail the most important planned encounters and simply sketch out and improvise the small encounters. This way you are not overwhelmed in preparation or play.
==Triggers==
Another type of planned encounter is the trigger. It can be used with a key or by itself. A trigger is a simple either/or or if/then type of statement. It is used for more interactive types of encounters, where the action of the event is what is important, such as the kidnapping described below.
The next episode occurs at 1 o'clock in the morning: If any character is still awake, he hears a muffled scream coming from the balcony of the room next door. If the characters investigate, they will discover two hooded men (6th-level thieves) attempting to drag a struggling young woman over the railing. One man has her firmly gripped from behind, his hand clamped over her mouth. The other is hoisting her legs over the side. A confederate waits with the horses on the ground below. If the characters do nothing, there will be a crash as she kicks over a flower urn, followed by a muttered curse and then the galloping of horses.
If the characters are noticed, the unburdened man wheels to face them, drawing two swords, one in each hand. The woman attempts to break free, only to be struck unconscious by the other man. The man on the ground quietly cocks a crossbow and aims it at the party, keeping an eye out for spellcasters.
Here everything is dependent upon previous and current choices of action. Is a character awake? Will the characters investigate? How will they react to the kidnappers? Each decision molds subsequent events. The characters might leap to the young woman's rescue or they might rouse themselves only in time to see the kidnappers gallop off with her tied to the saddle. Their actions could alter planned events. Coming to her aid, the characters rescue the lady. As DM you must be ready to tell her story. Why was she attacked? Who were they? Are there any clues the characters can find?
To write this type of encounter, first outline the basic sequence of events that would happen if the characters did not interfere. Next, think like a player and try to anticipate what the characters might do. Would they aid the lady? If so, you will need combat information—how the attackers will fight and what weapons and tactics they will use. What happens if the characters try to sound the alarm or talk to the kidnappers? What will the lady say if rescued? At least a brief note should be made to account for the probable reactions of the player characters.
As complete as you make them, triggers are not without their weaknesses. While very good at describing a scene, a trigger does not provide much background information. In the event above, there is no description of the room, the attackers, the lady's history, etc. There could be, but including it would be extra work, and description would also get in the way of the action.
A less critical problem is that DMs can't anticipate every action of the player characters. No matter how carefully a trigger is constructed, there is always something the characters can do to upset the situation. In the example above, what if the characters panic and a mage launches a fireball at the attackers? In a flash of flame, they and their victim are killed and the building is on fire. Prescient is the DM who can anticipate this event!
There is no simple solution for unpredictable players (nor would you want one!). As a DM you are never going to be able to predict every player decision. Experience, both as a player and a DM, teaches you what the most likely actions are. Beyond these you must improvise, relying on your skill as a DM.
==Combining Keys and Triggers==
Many DMs make use of a dual arrangement for preparing encounters. First they prepare a key, describing the appearance of the encounter locations, items in them, and other things that are relatively non-changing. Then they write triggers focusing on the characters and the actions.
When they need to describe a room, they rely on the key, while the trigger describes the plot of the adventure. Although this requires a little more set-up, this allows different events to happen in the same place or area, giving a feeling of continuity to the adventure and campaign.