Found the best way to make dungeons is just ask alot of people to put random stuff in. So here I am please comment what you would like to see in a dungeon. The more details the better. The play group is lvl 3. AND the setting is high magic. Thanks in advance to anyone that participates.
What is the expected max level of the dungeon, still PC level 3?
A room where the floor is a game of minesweeper.
I've always loved the idea where the loot is as deadly as the inhabitants. The idea for this comes from an adventure in an issue of Dungeon magazine.
Things like eversmoking bottle of acid fog, elemental gems hidden under pressure plates, animated chests (like a mimic, but actually contains treasure), bag of holding enlarged to completely encase a passageway (having fun cutting through that "leather" wall), runes that trigger a rod of wonder effect, and the like ...
One of my DM's put a water fountain in a dungeon that had a secret passageway below it. I love the idea of a fountain or some sort of body of water that has a secret within it.
A room containing a large cage hanging from the ceiling at the center. The cage is made out of wood and contains several rust monsters. The rust monsters are docile unless the adventurers open a poorly-hidden trapdoor containing a large pile of scrap metal. This gets the rust monsters excited, and they start frantically struggling to break out of the cage.
For bonus points, make the scrap metal a bunch of animated objects.
This door has an average lock (DC 25) with arcane lock on it (DC 35 to pick).
The door is made of ironwood and has hardness 5 hp 35 break dc 23
Written on the door in arcane runes are the following letters:
K D E N
Under the letters are further writings that are incomprehensible without read magic or comprehend languages.
If detect magic is used on the door it radiates abjuration and illusion magic.
Should a spell be used to read the further writings a DC 18 will save must be made or the reader is targeted with a suggestion to "Forget this message and leave this door alone" should they save they can read the following:
"Kahlam - the summoning spell I was working on went awry and I locked this up for lack of anything better to do with it - I don't know if it's dangerous or not play with it as you wish. Endo N."
Opening the room you find a 15x15 room with a softly glowing sphere floating in the center - (about the size of a baseball) the sphere gives off light equal to about a candle and it pulses a blueish yellow - almost as if it were a beating heart. The room is cold and damp - from the flickering light of the orb you can see the entire room is covered in protective glyphs meant to contain an outsider.
In the center around the sphere is a inwardly facing magic circle of protection from chaos facing inward.
The sphere is a connection to a chaotic neutral deity - if the circle is dispelled or broken the sphere 'adopts' whoever freed it and hovers over that person's shoulder. It answers questions with a yes or no answer and will respond to anyone that asks a question that it can hear - but only when it feels like it.
The answers it gives may be true, or not - but most likely it will give helpful advice until it is trusted - and then it will attempt to give answers that provide the most chaos from the result - regardless of the truth. Being part of a deity - there is no means of mortal magic to determine if the sphere is telling the truth, outside of asking another deity (via commune for example).
The sphere somehow survives any combat encounter regardless of area of effect or danger, however if the person who freed the sphere want to - they can grab ahold of it and crush it into a fine powder at any time (1000 gp of diamond dust result). This incurs the wrath of the deity if done (GM left to figure out how that plays out). With advice from sages and or divination magic the source of the divine can be discovered (but not through identify) most likely by asking a series of complex questions to determine celestial allegiance. Such an endeavor will take hiring a sage for at least a month. Once the source is discovered the player can track down any priest of the deity and transfer ownership by allowing the priest to 'adopt' the sphere.
The PCs end up in a room with 5 doors out; 4 of the doors lead to cages that have monsters in them (rust monster, stirges, swarm of bats, nilbogs, whatever).
Each door has a symbol above it, and there are 5 levers with 5 different symbols.
EDIT:
I've used this with 2 different groups. One solved it with a greataxe. The other figured it out pretty quickly, but not right away, so its difficulty was just right.
1: Game of minesweeper. Basicly trap door pit traps or click plates that activate 3D6 fireballs. Depends on level.
2: Room of holding(when you figure it out you can take the door with you) 100 by 100 room that contains a mimic full of level appropriate loot, 5 zombies armed with maces(appropriate plusses and animate the wielder when they die). A symbol of chaos on each wall that go off like a wild surge if looked at. 4 trap doors that contain the 4 types of elemental gems that activate unless you disarm the trap doors. The command word to cause the door to fold up into a 2 by 2 foot cube is on the inside surface of the door.
3: Secret fountain.
4: Hanging cage.
5: KDEN's cell.
6: Lever prison.
7: Pool room. One pool is full of boiling water. One is full of vicious fish. One is full of dry ice. One has some doses of healing potion at the bottom. One is full of acid with part of an artifact at the bottom. Ect.
A pit trap that has a pit trap in it that has a pit trap in it that has a pit trap in it that has a trampoline that bounces you back to the top so you fall through pit traps again.
Okay, a more serious series of responses:
I find encounters with weaker minions (like kobolds or goblins) that get raised as zombies mid-fight via Animate Dead are cool as f+&$.
One of my favorite kobold tactics is the "oh s+!% the adventurers are coming heeelp meeee" tactic. Y'know, where the kobold runs away and the adventurers give chase and stumble through all the traps and then get ambushed by the kobolds hiding in corridors and the like that say "Stupid humans fell for it again!" Use a combination of longspears, javelins, slings, and shortspears or handaxes + shields as the kobolds swarm the party to take advantage of aid another bonuses, flanking bonuses, and one mean surprise round. Preferably have them attack after the party fighter has already fallen into a pit trap or the party rogue has snuck off to find loot in the side corridor (which has a portcullis that slams down to separate whoever runs that way when they trip a wire).
Another fight could involve kobolds perched up on a wall with longspears and javelins and slings, pelting the party with stones and spears and then stabbing at them as they're forced to climb ladders to reach the kobolds. To be particularly rude have the kobolds kick the ladders down or use trip attempts on the party (with guisarmes instead of longspears) as they try to climb up the ladder. Also, the slingers / throwers should focus on the party's squishies and archers, obviously.
I hear that giant frogs are fun to fight at low levels. Being swallowed is a rite of passage.
If you want to be an utter ass to your players, a Rust Monster is technically CR 3...