Watcher's Keep

[LordHenry]

As the title suggests, I want to make a 1-shot dungeon similar to the Watcher's Keep from BG 2 (a dungeon with 4-5 levels, getting more difficult the deeper you delve into it, with a evil demon being imprisoned at the very bottom). I have handed out rules to my prospective players, and they will likely be lvl 10 (3 players will bejoining the game I guess).

What I wanna avoid though, is the 5 minute day. In a dungeon environment, (usually) nothing keeps the characters from clearing a room and then taking a rest for the rest of the day. Actually, this could be seen as the safest way making it less likely to die, so it would not be unreasonable from the character's perspective.
However, I told my players that I'd like this adventure to be a bit more challenging than your usual adventure, so they should consider that already when creating their characters.

So my questions are:

1. What are good and reasonable ways to avoid a 5 minute day in a dungeon environment, in order to a) make it more challenging because you can't just rest whenever you want and b) to make spellcasters less impactful compared to other classes.
2. How can I avoid (heavy) dungeon exploits, like teleports, stone shape etc to totally break what I prepared?

[NeoPhoenix0]

Roaming random encounters is a decent way to get rid of the 5 min day. Roll on a random encounter table every in game hour they spend in one place.

[CRtwenty]

1. What are good and reasonable ways to avoid a 5 minute day in a dungeon environment, in order to a) make it more challenging because you can't just rest whenever you want and b) to make spellcasters less impactful compared to other classes.

Random Encounters. Have the dungeon constantly patrolled so there's no real safe place to rest inside of it. If they stay in one place too long they'll inevitably attract the attention of something. If they Rope Trick have something notice the trick and set up an ambush for when they pop out.


2. How can I avoid (heavy) dungeon exploits, like teleports, stone shape etc to totally break what I prepared?

Have something around the dungeon that blocks Teleport magic while inside, if they leave the dungeon to Teleport away have it repopulate while they're gone with new creatures. Stone Shape can be easily avoided by having key areas be made out of metal or another material. Adamantine is a good one, especially on the lower levels. Let them cast it a couple times if they want, but if they start abusing it bring out the metal stuff.

You can also send incorporeal monsters at them. Dread Wraiths and Spectres laugh at silly things like Stone Barriers.

[Zombimode]

1. What are good and reasonable ways to avoid a 5 minute day in a dungeon environment, in order to a) make it more challenging because you can't just rest whenever you want and b) to make spellcasters less impactful compared to other classes.

You do not have to do anything special, really. You just need the mindset that a dungeon is not an arrangement of rooms whose inhabitants just patiently wait for the PCs to show up.


2. How can I avoid (heavy) dungeon exploits, like teleports, stone shape etc to totally break what I prepared?

Don't. If your characters have those abilities its only fair that they can use them for potentially good effect.
If your players use those (or any other) abilities to trivialize the challenge your dungeon was supposed to be, it just means that your dungeon actually wasn't a challenge for a party of PCs with the range of abilities as you PCs have.
To use a hyperbole: you don't expect a wooden door with a simple lock to suppose a challenge to a 20th level party, don't you? So if you want to challenge such a party, don't rely on wooden doors with simple locks. That doesn't mean that you shouldn't put wooden doors with simple locks anywhere in their way. It just means that the true challenge has to be constructed otherwise.
Also, think of resource management: sure, Stoneshape will open passageways in places that didn't have any formerly. But doing so costs a 3rd or 4th level slot.

[LordHenry]

Not being able to teleport inside the dungeon would actually make sense, since it is designed as a secret prison containing grat danger for the world.

You also can't leave the place once you are inside, so that is kinda similar.

I could let the ghosts of deceased adventurers who entered and failed wander the dungeon and pop up every once in a while.

However, they will need to rest eventually.. shuld there be areas where it is generall more safe to rest than others. Of course, then those areas should not always be accessable...