This one is for gamemasters learning to stock their first dungeons, a bit of straight-forward advice to make your life easier as you create and / or adapt adventures for your group.
Make the room fit the monster.
Now, this is more than just making sure that the dimensions of the encounter space match your adversary’s size. That’s just common sense. Dragons need a BIG room. Sprites less so (but room to fly around in is always advantageous).
And with the exception of magical enhancements, the entrance way has to accommodate its principal occupant. The naga might be content with slithering through the doggy door, but that ettin sure isn’t.
That said, let’s get to what this post is really about: Making the room fit the monster. By this, I mean that the encounter space should reflect its residents. I’m talking about dressing the room so it fits the monster’s ecology and purposes.
Let the monster manual, bestiary or adversary list for your chosen game guide you. Most monster listings include terrain as a descriptor. That is the first place to go.
OK, so let’s say the big book o’ beasts’ entry for the monster you’ve chosen lives in swamps. Does that disqualify it as a monster for your dungeon? Not at all. While it is true that swamp creatures like dry land as much as they do mud and pools, you should work with the water angle.
Create a room that is sufficiently damp to satisfy the swamp creature. Water collecting on floor, a pool overgrown with moss, roots dripping with moisture coming through cracks in the ceiling. You get the idea. Now this is a room that fits the monster.
But can you outfit an entire dungeon this way? Next, consider an alternative to terrain. Look at the monster’s descriptor for its preferences for treasure (and if is a beast, what it likes to eat. A meal is always as good as gold). If it likes gems, then it might prefer to live in volcanic vents, where gems form. If it has a hankering for mutton, then listen for the bleating from a nearby sheep pen.
Lastly, see if the descriptive text lists the monster’s motivations or things it values. A vampire with lust in its heart is going to be where the next party is. A priest of Ares likes to have lots of armor and weapons around. And the beefolk need lots of pollen.
You get the idea.
Dress your dungeon according to these three tips and you’re on your way to creating encounters that seem suited to your adversaries.