Relatively few spells in D&D 5e require a Charisma saving throw, and when they do it's often difficult to describe the in-game reasons for why they require such a throw.
One of my players told me that the Charisma saving throw for Banishment is essentially a check on the target's sheer "force of will" to remain in their present plane.
This clashes with my understanding of what a Wisdom saving throw entails. I've always imagined that the Wisdom saving throws for spells like Geas and Dominate Person were also a check on the target's "force of will".
Is there any narrative explanation for the difference between a Charisma and Wisdom saving throw? What is the in-game difference between Wisdom and Charisma in terms of willpower?
If both saving throws are related to willpower, then why are they treated as distinct saving throws?
To clarify: I'm not interested in the gameplay differences between the two saving throws. Clearly they have different purposes in terms of balance. What I'm more concerned with is how they relate differently to willpower.
Best Answer
It's unclear but...
Looking at the definitions provided for Wisdom and Charisma on the abilities page, there is not a clear definition of saving throws listed for the abilities.
Like you, I have also heard and read of Charisma as a sort of 'force of personality', though I'm having trouble finding that in a source book. In any case, I think what we need to turn to is the spell lists that require each type of throw.
For PHB Spells that require wisdom saving throws, we see things like: Charm Person, Command, Compulsion, Dominate Person, Enthrall, Hideous Laughter, and Polymorph.
For PHB Spells that require charisma saving throws, we see things like: Banishment, Calm Emotions, Planar Binding and Seeming.
Clearly there is some overlap, but I think we can draw some rough boundaries.
When making a Wisdom saving throw, you are retaining your attunement to reality by resisting magical effects that attempt to trick you into behaving differently then you would normally or take advantage of your unconscious. On a failure, your intuition has failed and you cannot correctly perceive the world as it truly is. An enemy is a friend or master instead. For the spell Scrying you are attuned enough to the forces of magic that you can detect an incoming spy and resist it.
When making a Charisma saving throw, you are using your force of personality to resist a physical alteration of the world. On a failure, your confidence is shattered so much that you are physically banished or restrained. You have lost your command of reality.
Ultimately though, you are correct. It is a fine line.