The description of Dispel Magic is as follows:
Choose one creature, object, or magical effect within
range. Any spell of 3rd level or lower on the target ends.
For each spell of 4th level or higher on the target, make
an ability check using your spellcasting ability. The
DC equals 10 + the spell’s level. On a successful check,
the spell ends.
At Higher Levels. When you cast this spell using a
spell slot of 4th level or higher, you automatically end
the effects of a spell on the target if the spell’s level is
equal to or less than the level of the spell slot you used.
Note that it specifically says it can end any spell. Geas doesn't provide any exception to this; it just says that it can be ended by the spells you listed. Compare it to, for example, Forcecage, which includes the following line:
This spell can't be dispelled by dispel magic.
If Geas was meant to be impossible to dispel with Dispel Magic, it would include a similar line.
Your questions:
Can a character under the effects of Geas cast Remove Curse on herself? YES.
Can this be prevented by saying "Bring me 100gp from the offering plate every day and don't cast remove curse on yourself?" NO.
How does this work? SEE BELOW:
Question 1:
There is nothing in the spell description stating that the creature is magically compelled to do, or to not do, anything, even disobeying the command you have given. What there is is a consequence for disobeying, which it explicitly states is possible:
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.
So YES they can cast Remove Curse on themselves. or in fact do anything else.
Question 2:
The geas spell description (PHB p.244) states that
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
This means that you can tell them to do something or tell them not to do something, but not both. Also it is singular, you can refer to only a single course of action. So you can't command them to not cast Remove Curse on themselves (or anything else) as well as the primary command.
So NO you can't prevent them from casting Remove curse on themselves in addition to the primary command.
Question 3:
I am going to rephrase the "How does this work?" question to something more specific: At what point does the target of a geas know it has had a geas cast on it?
The spell description states:
If the creature can understand you, it must succeed on a Wisdom saving throw or become charmed by you for the duration.
and that
A creature that can't understand you is unaffected by the spell.
This means that they have to hear and understand your verbal command to be able to follow it, there is no "telepathic" magical transference of meaning. This means the creature effected knows at least that someone has given it a command it can hear in a language it can understand at the time of casting. As stated earlier there is no magical compulsion to follow the command.
Do they know they have had a spell cast on them? The Rules answers 2016 state, using suggestion (PHB p.279) as an example, gives strong guidance:
You’re aware that a spell is affecting you if it has a perceptible effect or if its text says you’re aware of it (see PH, 204, under “Targets”). Most spells are obvious. For example, fireball burns you, cure wounds heals you, and command forces you to suddenly do something you didn’t intend. Certain spells are more subtle, yet you become aware of the spell at a time specified in the spell’s description. Charm person and detect thoughts are examples of such spells.
Some spells are so subtle that you might not know you were ever under their effects. A prime example of that sort of spell is suggestion. Assuming you failed to notice the spellcaster casting the spell, you might simply remember the caster saying, “The treasure you’re looking for isn’t here. Go look for it in the room at the top of the next tower.” You failed your saving throw, and off you went to the other tower, thinking it was your idea to go there.
Breaking this down you’re aware that a spell is affecting you if:
- it has a perceptible effect
- if its text says you’re aware of it at some point
You might miss that a spell is affecting you if:
- the spell is subtle
- you failed to notice the spellcaster casting the spell
Applying this to Geas:
- it does not have a perceptible effect at the point of casting and
- the description does not explicitly state you are aware of it.
- The damage done by the spell is psychic, in the mind of the target and that only happens at the point you go against the command and The spell has only a Verbal component, no handwaving or bits of fleece so it is subtle (a velvet wrapped hammer springs to mind)
So it is down to whether the character notices the spell being cast as to whether they know that a spell has been cast on them, up until they take damage and at that point it is whether they recognise the spell effect for what it is.
The PHB p203 describes a Verbal component of a spell as:
Most spells require the chanting of mystic words. The words themselves aren’t the source of the spell’s power; rather, the particular combination of sounds, with specific pitch and resonance, sets the threads of magic in motion.
This means that the words of the command given are not the only part of the Verbal component, at the very least the words have to be said at a particular pitch and resonance etc. So it will be down to the DM to set the difficulty for the target, or any other witness, to notice and recognise that a spell has been cast.
The target has to be aware of the command so no perception roll is required so as a DM I personally would base it on an Int(Arcana) roll (or Wis(Arcana) if you, like I do, use the alternate rules on skill characteristics with a different take on the information provided by a success). I'd suggest a difficulty of around 13 depending on the circumstances.
Best Answer
It is conceivable for a sorcerer to not know of a cleric spell to wish for in order to remove geas, per David Coffron’s answer. It’s a good point and I’ve upvoted that answer; it certainly is a difference.
But I find it isn’t a very compelling one. After all, not mentioning wish would take up less space, and thus save Wizards of the Coast money. I’ve worked in the RPG publishing business—publishers do not print things they don’t feel they have to print; it’s expensive. A corner-case like that doesn’t seem to justify the expense.
That difference may well be the only mechanical difference between the two approaches, but there are other differences between the two that should be considered—are more compelling, in my opinion, for answering the implicit question here—why this way and not the other way?
Player approachability
Players may not be familiar with wish when they get geas cast on them. They may not know that wish can copy remove curse or greater restoration. This is a far greater concern for Wizards of the Coast than the sorcerer not knowing about those spells—repetition is a big part of how human beings learn, and for many players, this may not even be a repeat. An accessible ruleset should be directing players to look into things that could be relevant to them when possible.
A continued tradition
Notably, this way is how D&D has traditionally handled wish—that is, wish has traditionally been listed as healing all manner of afflictions, even when those afflictions could be cured through spells wish was well capable of emulating. For example, the 3.5e version of bestow curse mentions wish alongside remove curse, which absolutely could have just been copied by wish. Longtime D&D players are used to wish being mentioned as a solution to all manner of afflictions. Failing to do so could give some of them to incorrect impression that something about wish has changed.
But most importantly, because wish is special
One might well point out that “the traditional approach” doesn’t really address the question but rather just shifts it—it wasn’t always the traditional approach, at some point someone first decided to do it this way. Player approachability might well have been the reason for doing so then, but there is another—more fundamental, and I would argue, important reason to mention wish explicitly when it could just be implied.
That is, a difference between mentioning wish explicitly and letting it be implied is that mentioning it explicitly mentions wish explicitly. This isn’t a means to an end—it is an end in and of itself. Mentioning wish explicitly all over the ruleset establishes, and reinforces, that wish is something special. In fact, “being special” is arguably wish’s raison d’etre.
Wish is special. Even among 9th-level spells, wish stands out. And that is because wish solves one critical problem. Sometimes that problem is not having the spell you need. But more often—both in game, and especially in narrative precedent—the purpose of a wish is to undo a dire malady. Think about it: when wishes come from a genie, power and wealth are common choices, but genies are special because they provide relatively casual access to the power of wishing. Otherwise, when wishes come true, they are usually the result of magic, the universe, divine forces, whatever, responding to some desperate plea—“save her!” “give him back!” and so on.
And that is why one of wish’s most important purviews is healing—because removing a deadly affliction, or death, is a huge part of what actually gets wished for. It establishes wish as the ultimate solution, the desperate last-ditch attempt to save someone. It comes at a cost, and at a risk, but it will get the job done.
So having afflictions list wish, over and over, even when it’s redundant to do so, as a valid solution, means that you keep seeing wish in these kinds of circumstances. It means readers can become familiar with the spell even if they never read it. They become aware that wish is out there, and that it is special.