More things I keep in mind when designing an expedition site. Traps, Monsters and Arcana are covered already.
1. They hold something worth finding.
2. They hide a mystery that doesn't always have an answer.
3. They change each time you return.
1. Interacting with them is the challenge, not finding them.
2. If they're secured, someone or something around here can open them.
3. If they're hidden on one side, the other side is found easily.
1. They have something to mess with.
2. They give you a clue about something else in the dungeon.
3. They reward further exploration.
1. It has character.
2. It has a complication.
3. It has a reason why you might want to keep it.
Let's put this into practice with a mini dungeon.
Black Noise Chapel
Sits on a soggy hill in Deep Country, a day's wagon from Bastion. Recently abandoned by the Cosmic Hiss Cult. They offer to pay 1g for each of their holy relics returned, or 5g for all four. They call these four artifacts The Quartet and are keen to avoid them falling into the wrong hands. These items all look like metal spheres. They won't give any details why they had to abandon their site.
There are two obvious ways into the chapel.
Main Door: Boarded up with planks that can be pulled off without much trouble. A black X is painted on front.
Escape Hatch: Connects a flooded tunnel in the chapel grounds to the trapdoor in Room 3. Crawling through takes just enough time that you can hold your breath safely.
Wandering Things (d6)
1: Powder Pup: 3hp. d6 paws. Like a large featureless dog made out of warm fake snow. Wants to get close to warm things and play but gets carried away and doesn't know its strength. Explodes in choking white powder if killed to reform in a few hours.
2: Powder Hound: 10hp, STR 14, d10 paws. Like a huge featureless bear made out of warm fake snow. Emits a bassy growl. Wants to protect the Powder Pup and get close to warm things. Explodes in choking white powder if killed to reform in a few hours.
3: Air Pulse Killer: 13hp, STR 14, DEX 14, WIL 11, Armour 1, Pneumatic Cannon (d10). Invisible humanoid being. Wants to seize Arcana, and use the Communication Hub to return home, which it doesn't know is impossible.
4: Scream: A deafening screech of noise coming from the Communication Hub. The Glass Shards in Room 1 shatter, causing d8 damage to those below.
5: Twitching Corpse: The body of a cultist is rhythmically shifting across the floor in spasms.
6: Bass Quake: Thunder shakes the chapel, causing falling debris to anyone that doesn't move to cover. (d6 damage).
All are Arcana of a sort. Each gives off its signature sound when held. They are all metal spheres the size of a cricket ball.
Rumble: Create an earthquake that will shake foundations and cause all nearby to stumble.
Powow: Remotely lift up to a pound of weight with pulses of noise. Pass a WIL Test to avoid hurling the object uncontrollably.
Fuzz: Creates a nice warm sensation in the holder.
Sigh: Anyone holding Sigh while it makes its noise must pass a WIL Save each turn or fall into a natural sleep.
1: Worship Hall
North: Door (slung open)
West: Wall (smooth metal, appears to slide open but only does so in response to a loud noise directed at it)
East: Reinforced Metal Door (locked, silver key on corpse in Room 3)
South: Door (Some white powder around, like fake snow)
Ceiling: Hanging Glass Shards (Hum slightly in response to speech)
Rows of Wooden Seats (some have been smashed by great force)
Stage (standing on here amplifies any noise, loud noises like gunshots could even cause damage)
2: Relic Chamber
Floor: Metal Hatch (Locked. Opened by the Pipes, but contains an electric shock trap that will shock anyone touching it for d10 damage, ignoring armour. This can be disarmed by the pipes. Contains Powow and Sigh)
West Wall: Clay Pipes (can be blown into to create a deeply irritating whistle, first blow unlocks the hatch with a click but arms the trap with a hum, second blow disarms the trap with a click, third blow resets the hatch)
Floor: Trapdoor (handle has been broken off, can still be opened with effort, corpses grasping at it)
Walls: Paintings (abstract shapes, moving slightly, any noise makes them move in time)
On trapdoor: Pile of Corpses (6 men, silver key on belt opens locked doors, one has Rumble hidden in a pouch, appear bludgeoned to death)
4: Communion Hub
South West: Door
South East: Door (Locked, silver key can be found on one of the corpses in Room 3)
North Wall: Metal Grate (answers questions with something between white noise, music, and speech. Attempting to engage it in its own language will enrage the Air Pulse Killer)
5: Sensory Drowning Pool
Pool (Water, Submerging barrages the bather with horrific noise, after the first turn, lose d6 WIL each turn, Fuzz is hidden at the bottom)