How to have players save against secret spells and traps

Question

I've been thinking about a method to utilize secret threats without removing player agency. This is especially important for when a character would be forced to make a saving throw by a stealthed enemy or a hidden trap without a perceptible effect. Are there any good methods of accomplishing this?

My goals include:

1. Preventing metagaming by avoiding player knowledge of the event

   In so far as the player may have his/her character continue more carefully if they know they failed a check against a Wisdom save (since that is the save affiliated most with curses, etc.). My players are very knowledgeable about the game and highly skilled in deduction; they have figured out what the rolls mean even with very little information.

2. Avoiding feelings of unfairness such as if I were to not allow them to roll

3. Maintaining the feel of player agency such as by not just rolling myself

To clarify what I mean by by player agency, at one point in time I discussed with my players the idea of me rolling behind a DM screen using their stats to avoid their knowledge and they said that, even though they do trust me, they prefer to know that they failed the roll leading to the negative effect rather than having me roll low on their behalf. This is the feeling I'm trying to avoid (even though mathematically it has the same result barring modifiers like Bardic Inspiration).

Example

One example that came up in my game revolved around detect thoughts. My players were exploring an abandoned Duergar mine and discovered markings of strange hexes throughout the mine. When my wizard casts detect magic followed by dispel magic on the markings, the Duergar imprisoned in the wall emerged and told them a group of dark cloaked beings had invaded imprisoning the Duergar and stealing a significant number of diamonds. My players began planning a way to track down and assault the thieves, but unbeknownst to them, a scout from the group was sent back knowing the adventurers were on their way to the mine.

While the bard did cast zone of silence, the scout knew the spell detect thoughts and would be able to learn their plan if they failed the save. The players then realized upon noticing that the enemy somehow knew the plan, that detect thoughts must have been used on that "random roll" I had them perform. I don't know if this factored in to their decision making as my players tend to avoid metagaming too much, but the bard and wizard did use mind blank "just in case" when they reached the old lair of the enemies they had tracked down (a cave that used to house an elder brain).

Answer 1

There's no need to roll the saving throw immediately. Wait until it has a perceptible effect, then have the player roll retroactively at that point.

For example, if they're inside a haunted mansion and an undetected enemy casts a curse on them which prevents them from leaving the mansion, they can wander around inside the mansion all they want and it makes no difference whether the curse worked or not. But, when they finally decide to leave, tell them "You were hit with a curse that confines you to this building. Make a saving throw to see whether it took effect."

Answer 2

Ask for the roll and do not tell them anything (yet).

It is pretty much a given at the tables I've played that the DM might ask a roll from the players, without specifying why. You can simply ask the player "Roll a d20" and when he asks "What happened?" reply something on the line of "Nothing attracts your attention" or "Nothing relevant". Then, if and when something would happen because of that roll, you reveal the relevant information, optionally saying "You threw for the save back then".

This has the advantage over postponing the roll that you know if the effect is there or not, for example, in case someone might notice active spells or any other reason.

If the players get used to it and start going meta by - consciously or not - expecting something whenever you ask for a roll out of the blue, start asking them to roll even when there is no reason to. Literally just ask for a roll and ignore it. If you make a habit out of it, it will force them to ignore random rolls and just focus on the in-game description of events.

Answer 3

You should have copies of your players' sheets, or at least notes of each player's modifiers. You can generate (with dice or a random number generator) 200 d20 rolls in advance, and have them written out on paper. When it's time for a secret check, just use the first on your list, apply modifiers, and you'll know if they make the save or not. Then cross out this roll and move down the line as needed.

I've been at conventions where every d20 roll for the entire module was generated in advance, including attacks. This removes opportunities for misunderstandings (temptation).

Answer 4

What I've done successfully before is Have each player roll 20 d20 dice rolls. I write them down in order. I keep the adjustments written down for each characters standard Saves. Then I roll a d20 for each character to establish where in the sequence I start using their rolls. So later in the game if I want a subtle save for the Half-Elf Wizard I consult his previous rolls. A will save is required, I had earlier started with his 8th roll so I just look at that dice roll apply his current will save adjustments and apply that to the save. It really works much easier and faster than you would think. Also it allows me to do things without a meta gaming player being the wiser.

This also puts it on the player as you are using the dice rolls he actually rolled earlier. So if there is a fail, then he rolled it before you began play. Boom, problem solved, mic drop.

Answer 5

Misdirection

If you want them to roll for a saving throw but not be suspicious, tell them the roll is for something entirely unrelated, or just ask for a plain D20 roll, then reveal a semi-related rumour they remember hearing or even spotting a discarded gold piece on the floor, they'll think they've won out on a sudden perception challenge.