Why is this monster here?
This is an important question. It is an obvious question for a designer or referee to ask.
I frequently find deeper concepts hiding behind the obvious. Let’s take a look.
There are many possible answers.
Because that is what came up on the random dungeon generation table.
Because I need a monster between 2HD and 5 HD to place on this level of the dungeon.
Because this is a crypt and you find undead monsters in crypts.
Because this monster is a minion doing an errand for the demon that has a lair in the 9th level of this dungeon.
Because this beat in “my story” requires that the players are captured and all of their gear taken from them so that they can progress to the next plot point.
Because first level characters need 2000 experience points each to get to second level. The dungeon is intended for a group of five characters. 2,000 x 5 = 10,000 I need 10,000 experience points worth of monsters and treasure. ¼ of the experience points come from monsters so I need 2,500 XP worth of monsters. I’ve already placed 2000 XP worth of monsters and I want one boss monster on this level so I’m using this 500 XP monster here.
Information/ Adventure Hooks
Because I need to convince the player characters that the goblins are a real threat to the kingdom. That way they follow the breadcrumbs back to the real threat; the cambion who has taken up residence in the old fortress on the edge of the haunted forest.
Real World Time Constraints
Because that is what the designer put here and I don’t have time to rethink and rewrite the encounter/adventure/campaign before my friends get here to play. I’ll go with it and see what happens.
When creating encounters, adventures, and campaign settings; I attempt to have a clear intention for everything I present to the players. Time to play is limited. Time to create material for play is limited. In the attempt to be time effective and time efficient; I am able to avoid unnecessary encounters that don’t add anything to the experience by continuously asking “Why is this here?”
“Why” produces answers that lead to other questions which inform the design choices you make as you move along with whatever you are building.
Asking a lot of questions about an individual encounter can produce some valuable insights and inspiration. This is particularly valuable if you use a random table that someone else wrote as a design prompt.
“Why” tells you “How.”
I try to put myself in the place of a group of players. I ask myself, “If I found this monster here; What questions would I ask the referee? What inferences would I make about the presence of this monster?”
I ask “Why is this here?” because my players are going to ask that question even if they don’t put it in precisely those terms.
The “Why” helps me when I’m thinking about how I will present an encounter. If a monster is present because it is a minion on a mission, then I can “show” and not tell the players by having the monster engaged in an action with context.
The players encounter a ghoul eating the remains of an adventuring party. After they finish off the ghoul, they notice the signs of blood trail. Something has drug a corpse away from the room. They follow the trail and find a flesh golem dragging a corpse through a passage.
This sparks all kinds of thoughts in the players; Why was the golem dragging the corpse? Where was it going? Who controls the golem?
“Why” helps you to shape the emotion.
It is hard to anticipate the emotional response of a player to an encounter but you can make a guess. I make a big effort to be mindful that the player is going to have a feeling when they have an encounter. I put a lot of effort into shaping the emotional landscape of my adventures and encounters..
If I am rolling on a random table and it comes up with a goblin I might reroll if I want the players to panic and run heedlessly into the next room where I’ve put a lethal trap.
“Why” applies to everything in your game.
Nothing exists in isolation. I live near Cleveland, Ohio. Why is Cleveland here? Because it is next two a large body of water connected to other large bodies of water which made long distance trade possible when there were no roads. The soil and weather here are good for growing lots of different crops. The water access provided a place for farmers to sell their surplus crops. You can apply this logic to your game.
Why is this town here?
Because the PCs need a place close to the dungeon where they can sell their treasure, get healed, and hire torch bearers.
Why can they sell treasure here?
Because there are merchants who will buy their treasure.
Why are the merchants here?
Because this town is safe, located on a regular trade route and a frequent stop of adventurers selling valuable goods that they can sell to wealthy patrons in a bigger city.
When I have exhausted the “Why” questions or feel I know enough about what this town is like; I know I need a watercourse or major road, sources of food, bandits, a lord who is taxing the merchants, a temple providing healing, unscrupulous people looking to fleece adventurers.
“Why is this here?” is a useful creative prompt for anything and everything that exists in your game.