If you're in my campaign, don't read this obviously :)

I have a pretty solid idea of what I want to build, but there are some details I'm trying to work my way through and I'd love some outside opinions if any of you feel inclined.

I'm trying to picture what a library in a wealthy merchant's manor would have that can be made use of for this. Maybe a decorative suit of armor. Plenty of books obviously, I imagine some paintings on the walls, one of which may well hang in front of the safe. Or maybe not a traditional safe with a handle and dial at all.

For someone to build a trap that would set off a fireball and burn down his own house, he'd have to be very confident that anyone bumbling the safe-opening process would be after something extremely valuable and he'd prefer to burn the house down around them rather than have them discover it. That's why I was thinking of putting some documents in the safe as well that would indicate his connection with the organized crime of which he is the boss.

Traps and puzzles in D&D suck and they do so for a wide variety of reasons. Instead of designing a trap or a puzzle design a problem. The benefit of a problem is you are not tied into any one solution like you are with a puzzle or a trap. Also a problem does not cause your players to break their suspension of disbelief like a puzzle does. I know this doesn't really help you in your current frame of mind but you might find if you follow my route that it will be easier. So the problem is ...."The players have to sneak into the crime boss wizard's library without being detected and find the hidden safe that possibly contains the control mechanism for the clay golem".

Done and done...

I will leave it up to you to put in the various magical and mystical wards...magic mouth, glyph of warding, alarm ....etc.

I've read your post several times in hopes I'm missing something and while it seems impolite for me to ask for help and then respond ungratefully when someone answers, all I managed to gather from your response is that you've denigrated the premise of my attempt while offering nothing whatsoever toward the solution for which I'm searching. "I'll leave it up to you" -- Thanks for your input :) Despite it being an opinion I've seen several times on these forums, I don't feel that the 5e rules are an inherent impediment when it comes to puzzles and traps and I think I can come up with one for this situation that will take the players a little bit of time and give them a sense of satisfaction at its completion. I'll continue workshopping it in my thread even if most of the responses in here end up being from me.

Now, rather than just *****ing, I've given this situation some more thought. If I have to err somewhere, I think I'll do it on the side of making the challenge a bit contrived in order to require several members of the party to offer contributions to get to their goal. At least part of the solution should involve searching, so the players will have to start by searching for the location of the container. I'm not as concerned about them picking the place where I've decided to hide it. It could be behind a painting, under a rug in the floor, behind a bookshelf, whatever. I want to make them search cleverly for it and settle on a hiding place where they think it would be.

The difference I'm coming up with on this situation and the puzzles I usually design in dungeons is that this one was clearly not intended to be figured out (well, it is intended by me as the DM, but not by the character in-game who created it) and more intended to punish someone trying to break in. In that regard it's more of a straight-up trap. I wonder if I should let them find a locked safe of some sort and try to pick it, but when they probe it, it gives a click and a rumble or a countdown of some sort and see how they react before the punishment comes. Maybe the door heats up and starts to sizzle or the party smells smoke and have a chance to run for it before it goes off.

I'll keep at this.

You know what? Auberginian did not offer me nothing whatsoever. I was wrong when I said that.

A glyph is much more practical than a fireball going off in the room. I am going to put fire glyphs all over the room and even into the hallways. While they are invisible at first, their presence can be detected by all but the worst attempt at an arcana check (DC10). This also addresses my problem of allowing the party to fail on their way to success.

Now I'm thinking party can do a search of the room and ultimately find (through whatever means of searching strikes me as the most inventive or interesting) three safes. The one in the middle has a dial and two keyholes while the ones on either side have hinges and a handle, but no obvious method of unlocking them. One will feel quite warm to the touch and the other will feel quite cool to the touch. My goal is to have one of the spell casters cast a fire spell on one and a cold spell on the other (doesn't really matter to me which combo) to open them and give access to a key in each. The dial on the center safe is a red herring. If the thief tries to pick the lock or fiddles with the dial, then there will be a loud click and a rumble and the glyphs in the room will start to glow red, becoming more and more intense over the next few minutes and if they don't figure out the hot and cold safe in due time, fires will break out. The fire will spread close to the heat-activated safe and it will pop open in a way that makes it obvious the heat was the trigger. That should prompt them to use a cold spell on the other.

So unless they solve it perfectly, the house will be on fire (minimal looting) and once enough hints have been dropped on them, they'll ultimately get the prize. And rather than punishing less-than-great puzzle-solving by denying the party the prize altogether, perhaps the control unit for the golem (ring, rod, headband, whatever) will be slightly damaged, making control of the golem a little more clumsy, tedious, or difficult to execute until the party finds a way to repair it.

I like how this is shaping up so far.

I like what you have so far with the keys, but I wanted to throw a couple more ideas out there about the fire and the golem's control unit.

Rather than having the fire trap just burn down the whole house, it might also be designed to kill the intruders. When triggered, it could seal the library and until the PCs can disable a hidden mechanism, they're stuck inside this burning room. Then they'll have to decide between finding a way to open the safe and escaping a fiery death. This also helps give everyone in the party something to do, as one or more PCs could be occupied with the safe while others rush to slow down the fire or unseal the doors. I've run a similar challenge before, and here's some actions and effects I cooked up for handling the fire.

This is how I modeled the fire's increasing intensity over several rounds. Feel free to adjust the damage and DCs as appropriate or to spread out the effects more if the fire spreads more slowly.

• Round 1 - Creatures in area of the fire take 1d6 fire damage due to choking smoke and intense heat (Dexterity DC 15 halves).
• Round 2 - Creatures take 2d6 fire damage due to smoke, heat, and the growing blaze (Dexterity DC 15 halves).
• Round 3 - Creatures take 2d6 fire damage and gain an exhaustion level (Constitution DC 15 halves damage, negates exhaustion).
• Round 4 - Creatures take 2d6 fire damage (no save). They also gain an exhaustion level (Constitution DC 15 negates).
• Round 5+ - Creatures take 3d6 fire damage (no save). They also gain an exhaustion level and lose an action this round (Constitution DC 15 negates).

Here are some actions the PCs could take to try and extinguish the flames, escape the room, and open and loot the safe. I had them roll Initiative and then take actions in order. Adjust the DCs as needed. You can easily extend this to other rooms if the fire begins to spread once the PCs escape the library.

• Open the Safe - The PC takes some action to attempt to open the safe (casting a spell to obtain a key, finding some other way to open the safe).
• Loot the Safe - Once the safe is open, the PC spends their turn grabbing everything they can (Dexterity or Strength ability check) or searching for something specific (Investigation check) like the golem's control unit.
• Attack the Door - The PCs can try to break the doors by dealing damage, but they're quite resilient (AC 17, HP 27, damage threshold 10; resists most damage types).
• Break Down the Door - Attempt to break down the door (Strength DC 21); using an appropriate tool (an axe) might grant advantage. This requires multiple successes.
• Find a Weak Point - Negates the door’s damage threshold on the next attack and grants advantage on checks to break it down (Perception or Investigation DC 17).
• Find the Mechanism - Find the mechanism that is holding the doors shut (Investigation DC 17).
• Disable the Mechanism - Once discovered, the mechanism can be disabled with thieves tools (Thievery DC 21). This requires multiple successes.
• Extinguish the Blaze - With a success, put out the fire in a small area. The check and DC depends on what methods the PCs use.
• Slow the Spread - With a success, the fire spreads less quickly. The check and DC depends on what method the PCs use. Grants advantage on saves against the fire's effects.
• Other Actions - The PCs might cast spells, use potions, or take other actions to buy themselves time.

Another idea - if the items in the safe and the wizard's house are so valuable, the PCs might not be the only ones there. Perhaps other thieves, maybe the members of a different criminal gang or a rival wizard and his henchmen, could arrive at the same time. If the PCs escape the fire and manage to secure the control unit, they could stumble right into an encounter with these other burglars. Also, if you're dead-set on having the mansion burn, you could have one of these burglars start the fire instead, accidentally or intentionally.

Now you're speaking my language. I love the idea of giving the other players something to do. I think the best puzzles are the ones that involve as many players as possible. I really like the idea of dealing with the doors after the players get sealed in the room. There's a decorative suit of armor standing near the wall. Now he'll be holding a battleaxe that just happens to be excellent for chopping at the door. I'm still thinking about something thematic for a mechanism to release the doors.

As for your last paragraph, the wizard was a local crime boss, so it would make a lot of sense his associates would definitely dispatch henchmen to the mansion to loot it and also to acquire potentially compromising evidence before it fell into the hands of local authorities.

EDIT: It occurs to me that you can treat the fire like a lair action without a monster.

TexasDevin,

When I reread my post I realized that I came across a lot more snarky than I intended. I was trying to suggest that perhaps your issue is in the fact you are trying to design a scene with one ideal solution. I was trying to impress that if you just created a situation that the players had to solve but that did not have a desired outcome or ideal solution built into it might help you out. However, it was not my intention to be rude and I am afraid that is how I came across and for that I apologize.

No apology needed. I ended up gleaning some inspiration from your post after all :)

After some thought, here's where I'm at for the moment on the great golem caper:

The players enter the mansion and work their way toward the library of the evil wizard (LZ). Upon entering, they take in the description, which they have seen before since they have been here once before. Shelves of expensive-looking books, many of them large and leather-bound, an overstuffed leather reading chair with a table next to it sit atop a thick woven rug covers much of the floor, absorbing footsteps of those who walk across it. A decorative suit of exotic-looking plate armor stands in the corner of the room holding a battle axe. LZ’s large dark wood working desk is opposite the entrance door on the far side of the room, organized despite holding various papers of work in progress. Behind the desk, a large painting of an important-looking elf scowls down to everyone in the room. Several more paintings hang around the room. The smell of books, parchments, and polished wood give the library its unmistakable atmosphere.

A DC10 arcana check of the room will reveal a number of glyphs and wards placed around the room, otherwise invisible to the untrained eye. More observant PCs (DC15 Arcana) will notice these are fire glyphs and wards that have a specific trigger other than proximity. A detailed investigation of the room (DC20) allows the party to locate three small metal doors behind a painting, under a rug (or wherever the party focuses their search). The doors are similar in appearance and size with the center door having two keyholes and a dial on it, much like the door to a safe. The other two doors have no handle, no keyhole and no discernable method of opening them, although they appear to be doors or panels of some sort as well. One of them is quite warm to the touch while the other is very cold. All three radiate a strong evocation magic to anyone detecting such things. If a fire spell is cast on one of the panels and/or a cold spell is cast on the other, the panel in question will pop open revealing either a red or a blue key. If both of these keys are inserted in the keyholes of the center safe, it opens up to reveal its contents. Any attempt to pick the middle door’s locks or to fiddle with the dial will generate a deep and substantial CLICK sound and a gentle rumble felt throughout the room. The wards and glyphs will them begin to glow dull red, then getting brighter.

Everyone rolls initiative. The party gets two free rounds to react to this as the glyphs become brighter red and begin to radiate heat. On the third round, they become hot enough to ignite any paper or wood there are in contact with, which include furniture and books. At this point, the door to the room swings shut quickly and locks with a loud click and previously unseen panels slide down over the windows to the room. The burning room now acts as a lair action.

• Round 3: The fire begins to spread, but not near the door yet. Anyone ending their turn within 5’ of the fire takes 1d6 fire damage due to choking smoke and intense heat (Dexterity DC 15 halves).
• Round 4: The fire spreads again, moving slightly closer to the door this time. Everyone in the room takes 2d6 fire damage due to smoke, heat, and the growing blaze (Dexterity DC 15 halves unless they end their turn within 5’ of the fire).
• Round 5: The fire spreads again, growing in intensity as it consumes the bookshelves and the books within them. Everyone in the room takes 2d6 fire damage and gain an exhaustion level (Constitution DC 15 halves damage, negates exhaustion unless they end their turn within 5’ of the fire).
• Round 6: The fire continues to spread, now consuming much of the room. Everyone in the room takes 2d6 fire damage (no save). They also gain an exhaustion level (Constitution DC 15 negates). The heat from the fire activates the heat-sensitive panel on one side of the safe and it pops open to reveal the red key.
• Round 7+: The room is now a blazing inferno and there is no easy way to escape the heat and smoke. Everyone in the room takes 3d6 fire damage (no save). They also gain an exhaustion level and lose an action this round (Constitution DC 15 negates).

As the fire spreads, I will drop some hints as to what the party members could be doing about their predicament.

• Keep working on the safe – Opening the safe swings the door and window coverings open, revealing that the entire mansion is aflame as well. Time to get out!
• Attack the Door - The PCs can try to break the door by dealing damage, but they're quite resilient (AC 17, HP 27, damage threshold 10; resists most damage types).
• Break Down the Door - Attempt to break down the door (Strength DC 21); using an axe such as the one the armor carries would grant advantage. This requires three successes.
• Find a Weak Point - Negates the door’s damage threshold on the next attack and grants advantage on checks to break it down (Perception or Investigation DC 17).
• Extinguish the Blaze - With a success, put out the fire in a small area. The check and DC depends on what methods the PCs use.
• Slow the Spread - With a success, the fire spreads less quickly. The check and DC depends on what method the PCs use. Grants advantage on saves against the fire's effects. Next round will be treated as the same round for purposes of the spreading fire.
• Do something else interesting.

When opened, the safe contains a number of plot continuation documents as well as a scepter-looking device that is held in one hand. Once attuned, the holder can speak commands into it and the golem will do its best to obey them. Complex commands will easily confuse the golem. The device might be damaged by extended fire exposure, requiring a persuasion check whenever a command is issued until a proper expert is located to repair the device. Each of the two keys are made of an unusual non-metal material in blue or red respectively and have a small gold value to it.

If the party somehow manages to work the safe without springing the trap, they will be stumbled upon by a group of LZ’s former organized crime associates who snuck in looking for the same things the party seeks. There will be a confrontation and at least one of the baddies will flee and start several fires in the mansion to burn the place down. Better to destroy the evidence than have it fall into the wrong hands.

This looks great. I hope your players have a blast with this (no pun intended). A couple small suggestions:

• Maybe give your players a chance to notice the panels that will seal the doors and windows with a very good Investigation check.
• Take care with the round delay in activating the trap. The potential problem I can see with this is that some PCs might leave the room. You'll want to consider how PCs who are stuck outside the room might be able to help those who are trapped inside.
• Consider the worst case scenario: the PCs are trapped and unable to get themselves out. Will you let them die in the blaze, or is there some hope they might escape? Perhaps the criminals prove to be their saviors (accidentally and ironically).
• On the same note, I'm not sure what level your PCs are, but I'd run the math on the damage and make sure they won't all be knocked unconscious early on by unlucky rolls.

My reservations are mostly because when I ran a similar trap, I did almost kill the PCs, but they made a harrowing escape in the end. This was mostly because they rolled very poorly on their ability checks during the challenge, but it's something to keep in mind. My players ended up enjoying it in the end, despite the near-death experience.

I had decided on having them notice the panels on a DC20 investigation check. I guess I didn't work that into the write-up. I considered the ramifications of one or more players outside the room when the trap snaps shut. I kind of like the idea. I imagine they would be focused entirely on destroying the door in that situation, which is probably for the best anyway. But you know how players are. If you think they are going to do something, they will probably do something else so who knows? My intention is to make it moderately challenging for them to escape the fire and more challenging to escape the fire with the prize. If it all falls apart and they don't get the golem, then so be it. It doesn't hurt the story as it was something I never anticipated in the first place.

The damage from the fire is harder to predict. The lowest hp character (the sorcerer) is a a tiefling so at least he will have fire resistance. The group has a cleric and a bard who can do some healing. They also have a few healing potions they can use to stave off the fire, but potions really only buy you a round against increasingly bad odds. What might be more interesting are their various attempts to deal with or put out the fire rather than escape it.

My biggest fear in this situation is that the party will attempt to loot the mansion on the way in, thereby forcing me to have to come up with a bunch of banal freebies for them before they even set off the trap.

That makes sense to me. The damage is probably fine, as even if a PC manages to fail all their saves and doesn't have resistance, they'd still only take on average about 35 damage by Round 7. But if one or more PCs are knocked unconscious, you might end up with a bit of a cascading effect where rescuing unconscious PCs makes escape that much harder. But I think this is really only going to be a problem if your PCs are very low level, have on average very low HP, or don't have sufficient access to healing.

As to the looting problem - I imagine if the wizard put so much work into this trap, then anything truly valuable is in the safe. You might consider handing out a couple common magic items (and maybe one or more uncommon ones) or some unique mundane items befitting a crime boss. Just enough to be interesting without being gamebreaking. But anything that the PCs are going to sell anyway doesn't really need to be described except in very general terms.

The joke's on me. Today's session finally had the long-awaited and much-prepared-for encounter in the library. The players found the safe doors and noticed the arcane sigils around the room. So far so good. Then they put their hands on the panels and felt one was hot and one was cold. They cast firebolt at the hot one, and chill touch on the cold one. Both panels popped open, they got the keys, unlocked the main safe, and retrieved the contents. The whole thing took about a minute.

Just when you think you have something planned out, the players always throw you for a loop :) No worries. This will pop up later in the game since I spent so much time workshopping it and tweaking the process just so.