Let's say a wizard casts Geas at 9th level on a Cleric and says "Bring me 100gp from the offering plate every day."
Can the cleric basically just wave her hand, cast a 3rd-level Remove Curse spell on herself, and end the effect? Furthermore, can this be prevented by saying "Bring me 100gp from the offering plate every day and don't cast remove curse on yourself?" Even then, the psychic damage doesn't seem like much of a cost.
By RAW it seems that this is possible, but in terms of balance this makes a simple remove curse unbelievably powerful.
How does this work?
Best Answer
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:
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
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:
and that
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:
Breaking this down you’re aware that a spell is affecting you if:
You might miss that a spell is affecting you if:
Applying this to Geas:
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:
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.