Secret door and trap DCs in Tomb of Horrors vs Expertise

Question

Normal skill checks

The standard DCs for skill checks, for example for discovering secret doors with Wisdom (Perception) or Intelligence (Investigation) is given on page 238 DMG under Typical DCs:

Task	DC
Very easy	5
Easy	10
Moderate	15
Hard	20
Very hard	25
Nearly impossible	30

This makes sense for normal characters. If they are proficient, even at mid levels they might have +9 in those skills, enough to make detecting hard to detect door close to a coin flip. Even at highest levels, they might have a stat bonus of +5 and a proficiency bonus of +6, for a total of +11, making it barely possible for legendary heroes using their strongest abilities to achive a nearly impossible task on a roll of 19 or 20, and having a shot somewhat better than fifty-fifty for a hard task. So you can just use what it says on the tin to set DCs for your secret doors and whatnot. Hard to discover secret door? DC 20.

Expertise breaking bounded accuracy

That changes with Expertise. For example, a rogue or any character with the Skill Expert feat in one of these skills would have +8 bonus from Expertise and by level 11 gets the Reliable Talent which sets proficient skill check rolls smaller than 10 to 10. Their minimal result is already 23. In practice it may be only 22, as they typically put their best ability score on Dexterity, but either way, they would discover all hard secret doors automatically. In tier four, they most of the time would discover even that nearly impossible secret door. (There are uncommon magic items like eyes of the eagle that could turn this into always, but by then you maybe have better things to do with your attunement slot).

Now, there are other ways to detect secret doors, with uncommon items like the wand of secrets, or with spells. But those are not always on.

Tomb of Horrors

Tomb of Horrors is an infamous adventure light on combat encounters, but heavy on traps and secret doors. In the original AD&D version, normal characters had a 1 in 6 chance (about 17%) and elves had a 2 in 6 chance (about 33%) to detect secret doors, and everyone had a 3 in 6 (50%) chance to detect pit traps -- when tapping for them with a pole. The 5e version of this says:

A character who succeeds on a DC 15 Wisdom (Perception) check discerns the edges of a pit's lid.

With DC 15 even normal skilled PCs with max stat have a 75% chance to detect these features. For a rogue of level 11, it is automatic detection. This DC clearly makes it much easier than it was in the original.

Now, if I want to replicate the original experience more closely for Tomb of Horrors, I can of course increase that DC to make it approximately as deadly as the original. But to what target number?

I don't want to adjust this on the fly in reaction to the party composition -- that just feels like cheating to negate the investment party members may have made into their characters' abilities.

What may be a challenge for a group without a rogue might be near automatic success for one with a rogue, and what might be challenging for one with a rogue might be near impossible for one without. I wonder how to deal with this? What number would you set the DC to as an adventure designer to create a challenging experience, given there is Expertise in the game, but you cannot know the party composition?

Answer 1

I wonder how to deal with this?

You can’t within 5e Dungeons and Dragons.

Tomb of Horrors is built for a different game and a different attitude. 5e assumes the rogue finds the secret door; 1e assumes the rogue’s player finds the secret door with the 1(2) in 6 roll as a lucky break if they don’t. The onus is on the player to work out that there must be a secret door there and then experiment to open it.

You also have the wrong attitude - you say you want to “challenge” your players. No. The correct attitude is that you want to kill your player’s characters over and over until they cry like a 4 year old whose lollipop you just stole. And then you laugh. This an S&M dungeon - the DM gets the S, the players get the M.

Failure is not merely an option here; it’s a near certainty. Back in the 80s our group had several attempts at this dungeon. Many PCs died. The furthest we got was the chapel - about 1/3 of the way through. Based on what I’ve read, we did better than most.

If you want the authentic experience put your 5e books back on the shelf. Get a copy of OSRIC and play it under the original conditions.

It was frustrating, painful, rage-inducing and enormous fun. But, it’s not a dungeon for everyone; particularly not these young punks with their “character development”, “backstories” and “motivations”. As for giving a character a name? What’s the point? They’ll be dead in a few hours. Oh, and get off my lawn!

I’m running the Temple of Elemental Evil with OSRIC and my players are enjoying it. 1 player is an old companion from my original ToH play through so we have that PTSD in common. The other 5 have only ever played 5e D&D and some non-D&D RPGs. They say they are enjoying the system because it doesn’t slow the game with things like rules and skill checks. Of course, ToEE is a cakewalk compared to ToH. Like the difference between a long hike and the Bataan Death March.

Or, https://rpg.stackexchange.com/a/65107/6203. I never claimed to be consistent.

Answer 2

They're still going to die

I've run ToH in 5e for a large group of adventurers (about 7, but only about 4 at each game night). While sessions usually only had about 4 players, we did end up with a wide range of races and classes - including rogue. And, of course, lots of new character creation and opportunities to see new builds.

Characters who had expertise did not impact the survivability of the group or themselves - and characters still died with regularity. I saw no issues with the DCs as they were set by the module with regard to rogues or anyone else with expertise ploughing their way through because it's "easy." There is no easy button in ToH.

There isn't a need to adjust anything, this module is deadly. My issue with it is that it is deadly from randomness, and not from player agency.

Caveat Emptor

I need to be honest with you, and I know you are aware of Gygax and his "idiosyncracies", but this really does play like a module built by an awful DM to kill his players. And it wasn't even for me as DM to run something like that. While no one actually said "please stop this" I did ask everyone and they still said to keep going. But when I finally pulled the plug and ended it early, it was too late. Players had left the game and did not return and while they didn't say why, I'm pretty confident it was this module. It's just set up to not just be a challenge, but to be a challenge in which you can't prepare for or make any sort of educated guesses to help your characters. It's a death trap, and not just as a game, but possibly for a group.

And while we all have different playstyles, I was pretty sure my group would be into this. While it was a large group in total, there were only about 4 concurrent game night players. The size of the party really didn't effect my experience with this - the way the module itself ran and how both my players and myself reacted to it is what drives this answer. Before running ToH, I did my research. I understand what we were going into and talked about it with the players. Everyone was on board with the idea - but when the rubber hit the road and the adventure was played, I realized that while they said they were having fun, I could tell that they weren't - and I wasn't either.

As long a table really understands (and they won't until they get punched in the nose with it) how much is out of their own control and death isn't really from their own choices, then give it a go. However, please keep on checking in with the table and yourself about how you feel playing it.

Answer 3

No rogues is better than bad rogues.

Inspired by the adage "no gaming is better than bad gaming", I offer you the idea that just banning rogues is better than finding a way to nerf them in some way. So just ban rogues when you pitch your game. See my answer to this question for how I've done this before, How can I limit (but not outright ban) exotic races? :

I have a similar issue that I have handled this way. I don't like running Tier 1 and 2 play with Aarokocra. I don't like having to design encounters for a character with an innate, non-magical 50 feet flying speed during the early game. So when I pitched my game at my local game store's LFG board, I literally just wrote:

Curse of Strahd, Saturday evenings, no Aarokocra.

And when I got the group together for Session 0, lo and behold, no one brought an Aarakocra character sheet. My players had bought in to my stipulations before they even got to the table for Session 0. This way is easier than convincing someone not to play a race they want to play.

So just ban rogues and then you don't have to change anything about the adventure. That said, telling the players you're going to nerf rogues may have the same effect, and you still won't have to change the adventure. However, if you ban rogues in your pitch, no one will bring to session 0 an expectation of playing a rogue, so that is the better method.

I’ve singled out the rogue here because that seems to have been your focus in writing the question. But it applies to other things too. Bards get expertise and might throw your game off. The idea here is simply pitch the game you want to play and people who want to play a different game won’t show up.

Answer 4

Lightly Obscured Traps

Inflating the DC might make player's feel like the challenge is unfair (being told a 25 is a failure is more than a little surprising). To bring back the difficulty, without raising the DC, you can lightly obscure the traps by placing them in Dim Lighting or in a foggy area.

When trying to spot these traps, characters will be making perception checks with disadvantage, and will have their passive perception lowered by 5.

Rules on Vision & Light

In a lightly obscured area, such as dim light, patchy fog, or moderate foliage, creatures have disadvantage on Wisdom (Perception) checks that rely on sight.

Rules on Passive Checks

Here's how to determine a character's total for a passive check:

10 + all modifiers that normally apply to the check

If the character has advantage on the check, add 5. For disadvantage, subtract 5. The game refers to a passive check total as a score.

Dim Light is a very trivial challenge to overcome at any tier of play. Darkvision, a torch, or the Light cantrip will remove this obstacle almost entirely. So instead of Dim Lighting, I suggest a "magical fog" that doesn't disperse with wind.