Quick question on homebrew

[Ghostwidow]

If I have a group of adventurers, and I want to curse them through home-brewed Rune Magic, in that they will all be hit by this curse while sleeping, and wake up with a mark in their body which negates their dark-vision ( again home-brew rune magic curse ) what saving throw would make the most sense against this? Wis? Dex to avoid being branded? Con? Would it be fair to bypass the saving throw in that they do not get one?

[Rynjin]

Int is usually used for dream stuff IIRC, but if you want it to be a plot thing you can just tell your players up front "Hey someone is gonna do some voodoo on you for plot reasons, you don't get a save". Give them all Inspiration or something to compensate for it.

Don't try to be all mysterious about it, people get pissed off that way. Just be open that they're getting railroaded and people are usually chill.

[Tawmis]

If it's a story element, and your players get that, then they should be good with it.
I'd let them know (through NPC or something) on how to eventually break the curse.

So, for example in my games - most of my players are new to D&D.
So, I currently only allow "Player's Handbook" spells and such as being available. So they wouldn't get overwhelmed with all these books to look at spells from, potential class variations, etc.
I explained, there would be a quest to shatter a sphere that contained all this ancient magic (the other books), and when they do so they can remain the same class but change the variation of the path they took originally, if they wanted, as their minds are filled with knowledge and magic.
So one of the players donned a gauntlet - that was cursed with an "ancient magic." So the gauntlet does a number of things, since it's an evil ego, and will try to "redirect" heals to her party to healing a great evil. And only does so in the presence of strong evil (so a band of goblins it won't do anything, but in the presence of a powerful Necromancer, it might try to heal the Necromancer, rather than the party - and she has to do a WIS save, which - as a cleric she's good at - it's more for fun and suspense). I explained, it would require unleashing the ancient magic to remove the gauntlet, as a way to ensure the party will eventually make their way to where this sphere is located, according to legend.

[Catullus64]

I wouldn't give a saving throw, at least not for the initial effect. Maybe once the players have figured out something about the source of the curse, and begin taking actions to reverse it, they can then start making saving throws at a rate relevant to the pace of the adventure; if it's combat-heavy and this discovery comes while in active danger, every round; if it's slower-paced, every hour, or in some circumstances daily. Lack of Darkvision isn't that big of a disability, to the extent that I often like to make replacement features for races that have it. Once the saving throws start kicking in I would say Intelligence.

That being said, how many members of your party actually have Darkvision?

[Keltest]

If its relevant to the plot in some way, dont give them a save, just tell them flat out its a plot device. If you give them a save, they might pass the save, in which case your plot hook has suddenly lost a lot of potency.

[JNAProductions]

This sounds like it could backfire.

Why exactly is this curse targeting their Darkvision?

[J-H]

This is magical but it targets their body's natural functions, so I'd make it a Constitution save.
Consider targeting as well - how is the enemy seeing them to target them? Scrying? Can whoever is on watch (someone will be) detect it?

[Ghostwidow]

Its part of a long going storyline, but the presence of this “spirit” that are trying to figure out, has been after them for some time now. They have an encounter coming up and taking away their darkvision ( only if for a short amount of time ) will make the encounter more challenging for them and make them change from their normal tactics and think outside the box. Plus, it kind of goes along with other hindrances the spirit has been bringing upon them thus far. All but one member of the party currently has dark-vision.

[JackPhoenix]

Blindness/Deafness is similar in effect, if more severe and time-llimited. I'd base it on that and give it Con save. Dex doesn't make much sense when they are sleeping (and autofail Dex saves anyway). Wis is possibility, but if it's plot-related, no save may be fair... you know your players and know better how they'd react to something like that.

[Burley]

If I were to do it, I'd do what's already been said: Let the players know they're being branded and provide no save.

But, now that they're branded, you can do Save vs. Effect stuff to your heart's content. They're cursed, now they need to Con vs. Dark-blindness before they go into the cave. Maybe when they're trying to speak with some official, Con vs. Deafness/Muteness.

I like the idea that this spirit has cursed them and I'm rolling with it imposing relevant curse effects for whatever they're about to do. Not all of them will be afflicted, maybe none of them. But, it'd be something they can expect to happen and may mix up how they normally handle situations (from carrying a torch to having the barbarian do the negotiating).

[Keravath]

Giving it a save is preferable if you don't mind the possibility of some or all of them saving. It is more fair to the players in a sense though having the effect happen as part of the story is also possible if you justify it.

Also, you can set the DC high but not impossible (e.g. DC20 Con save to resist the curse) to control the odds. Depending on the character levels a DC20 would typically be anywhere from 10% to 35% chance to save depending on con score and proficiency.

Narratively, you could describe it as feeling a chill that makes you shiver for a second then it goes away. Anyone who failed notices a cooler part of their skin with the mark on it as it slowly warms up. If they aren't using lights at their camp then the ones who lost their darkvision might initially think they are blind.