Geas spell states:

You place a magical command on a creature that you can see within range, forcing it to carry out some service or refrain from some action or course of activity as you decide. If the creature can understand you, it must succeed on a Wisdom saving throw or become charmed by you for the duration. While the creature is charmed by you, it takes 5d10 psychic damage each time it acts in a manner directly counter to your instructions, but no more than once each day. A creature that can't understand you is unaffected by the spell.

For the sake of the argument, and for context, let's assume some quite nasty command, such as "go burn your house down right now". And the target failed the save.

Does the target of the spell somehow (magically?) know they will be badly hurt (usually lethal for most creatures of CR 1 or below), if they act directly counter to the instructions? Or is it up to the caster to tell them, that they'll probably die if they disobey? Do they believe automatically or is it going to be Intimidation/Deception/Persuasion roll?

If target does not automatically know (or believe) what happens if they act wrong, how does the forcing actually work? At least Suggestion explicitly says target will carry out the suggestion to the best of its ability, but Geas has no such explicit text.

There's this related question, but it does not address how the target actually knows to obey.


3 Answers 3


They might not know, but you really should tell them...

The Geas spell is D&D's version of the classic folklore trope of being cursed by a witch or wizard or compelled to perform a quest. In both cases the caster is trying to force some sort of behavior, so presumably it is in the caster's interest to tell the victim of their peril. Otherwise, it would just be some sort of delayed damage spell. This will likely just kill the victim, unless they are tough and/or figure out really quickly what is going on on their own.

While it might be funny to an evil wizard to curse the king with a Geas that triggers if he ever eats another bite of food, this probably isn't going to be how most casters will use it. If you really want the trespassing paladin to fetch you a magic staff from the dragon's lair as punishment, you will need to tell them what you have done, where the dragon's lair is, and what the staff looks like. Most casters with a high intelligence will realize this, and evil ones might cackle about it as they do so.

If you really want to give a nod to folklore, lay out the Geas in rhyme:

In twilight's grip, you must roam,
Cursed to seek the dragon's home.

A black beast lurks in shadow's veil,
That guards a staff, the wizard's wail.

A clash of wills, a battle dire,
Steel against the dragon's fire.

Within the lair, the goal you'll find,
To break the curse that fate entwined.

The spell loses a lot of its power to compel if the target doesn't know what is happening.

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    \$\begingroup\$ We prefer to avoid code block formatting for accessibility reasons. Please use the quote block format instead. \$\endgroup\$ Commented May 14 at 8:36
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    – Roger Hill
    Commented May 15 at 19:27
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    \$\begingroup\$ That should be more faithful to your original composition. Also, I’m sure you have no idea the extent to which I am involved in improving many features of the site and network, including accessibility related features. \$\endgroup\$ Commented May 15 at 19:59
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    – Mołot
    Commented May 15 at 21:51

The rules don't say

Personally, I'd go with the mythological basis for geasa when the rules fail to specify and there are serious consequences if the spirit of the spell isn't involved. In Irish & Welsh mythology, the concept of a geas usually involved your "doom" befalling you if you violated the geas (extreme dishonor or death typically, but the exact consequence was rarely spelled out, and was sometimes simply implied by the mere fact of being put under a geas). I'd generally rule that the target, if not told otherwise, and not aware of the exact mechanics of the spell, knows the geas is important, and failure to follow it will bring personal disaster (without knowing it's possibly lethal damage).

Geasa weren't typically handed out as threats, just rules laid down without the target necessarily volunteering for them, but they were accepted nonetheless; the fact that the target is Charmed (and therefore unable to harm the caster, and tending to treat the caster as someone to listen to, given the social skills advantage) is in keeping with this. The target, having failed their save, believes on some level that the caster has a right to impose this duty, and that failure to follow it will lead to their doom.


They do not know

The spellcasting rules under Targets (p. 201 PH) say

Unless a spell has a perceptible effect, a creature might not know it was targeted by a spell at all. An effect like crackling lightning is obvious, but a more subtle effect, such as an attempt to read a creature’s thoughts, typically goes unnoticed, unless a spell says otherwise.

The spell does not describe any perceptible effect. As the target would not even know it is under a spell, they certainly would not know of the effects either.

It would be up to the DM to decide that "forcing it to carry out some service or refrain from some action" means they feel some kind of compulsion. The spell does not say that, and you could just as well say "forcing it" is achieved via the punishment if you do not obey.

If they observe the act of casting they might be able to make a Spellcraft ability check, and if they succeed and know the spell, realize the effect it will have. In such a case, as hit points are a construct for play, not something experienced in-character, the creature probably would know that the spell "nearly certainly will kill you" or "might kill you" or "will harm you and cost you mental stamina and resolve", depending on the amount of hit points they have.

Even if they do not make the check, they might understand that a spell was cast on them - the verbal component is different from the command that you can issue after the spell is successfully cast. It's up to the caster to warn them of impending doom if they do not follow through, and the caster does have advantage for any social skill check for that, because the creature is Charmed.

On a historic note, the Harold Shea stories by L. Sprague de Camp & Fletcher Pratt were cited by Gary Gygax multiple times as one of the major influences on the game. In "The green magician", Harold's wife Belphebe is placed under a geas that a man trying to get intimate with her will fold over from pain of stomach cramps, without her or Harold even realizing it until the effect happens.

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    \$\begingroup\$ "Harold's wife Belphebe is placed under a geas that a man trying to get intimate with her will fold over from pain of stomach cramps" Wait, so... She got geas-ed, but it affects the men "around" her?? \$\endgroup\$
    – Malady
    Commented May 14 at 14:44
  • \$\begingroup\$ @Malady Yes, its like that. There are also other geases in the story like the Irish warriors being afraid to drop dead when seeing someone naked — that's more on them, I guess. \$\endgroup\$ Commented May 14 at 14:46
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    \$\begingroup\$ I disagree with the premise. First off, the spell has a verbal component, and requires the target to understand the caster to be effective; the clear implication is that the nature of the command is communicated to the target, which is a pretty clearly perceptible effect. I find it highly implausible that the verbal component of Geas (which also doesn't have a material or somatic component) is indistinguishable from simply making the demand in normal speech. \$\endgroup\$ Commented May 15 at 4:29
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    \$\begingroup\$ Further, it would defeat the apparent purpose and design of the spell, and IMO cause serious balance issues. If you could mislead the target about the nature of the Geas, it could plausibly be turned into a straight up 5d10 psychic damage spell, with the potential for a daily repeat. On the other hand, if it's known in the world that the Geas spell exists and you can't tell that you're under one or what you're commanded to do, it becomes far to easy to bluff that you've cast it. \$\endgroup\$ Commented May 15 at 4:30
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    \$\begingroup\$ If you want them dead, without obvious pyrotechnics (read: sticking to single target psychic damage), a simple upcast Mind Spike would do roughly the same average damage on a failed save (27, vs. 27.5 for Geas), with the same visibility (arguably less; pure somatic components not being visible if they're not looking at you, while verbal components can be heard from any direction), same range, same saving throw, costing only one action. And unlike Geas, it'll do half damage even on a save, and on failure, even if they survive it, you can track them for up to an hour and finish the job later. \$\endgroup\$ Commented May 15 at 13:29

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