Can magic users control arcane energy in ways other than the spells they can cast?

Question

Situation that arose: A level 1 Wizard decides to interrogate a Goblin. He wants to "slightly shock him with electricity" to wake him up. The only lightning damage spell he knows is Shocking Grasp, but he isn't trying to cast the cantrip, he's trying to summon a much weaker form of shock, just to zap the creature back into consciousness.

My question is - to what extent are magic users 'in tune with the Weave'? Can Wizards only summon magical energy via their known spells or can they manipulate energy at will for smaller, role playing effects? I'd think it's likelier for Sorcerers to be able to do that, but not Wizards. Is there any official material that explains these relationships better than the PHB?

Answer 1

No, at least not by default for spells

D&D uses the Vancian magic system. One of the characteristics mentioned there is:

Magical effects are packaged into distinct spells; each spell has one fixed purpose. A spell that throws a ball of fire at an enemy just throws balls of fire, and generally cannot be "turned down" to light a cigarette, for instance.

(5e spells can be cast as long as you have spell slot, a bit different from the original Vancian magic, which is one use only per prepared spell.)

This is similar to what the Basic Rules say about what a spell is:

A spell is a discrete magical effect, a single shaping of the magical energies that suffuse the multiverse into a specific, limited expression.

You can then compare it to a computer program, and find that a spell is somewhat analogous to a computer program:

A computer program is a collection of instructions that performs a specific task when executed by a computer.

So by default, spells only do what they say they do. If the description says it can be toned down, it can. If the option is not provided, it can't be toned down.

Maybe your campaign is different

How magic works in your campaign might be different. Tell your intent to your DM and let them decide. These are starter ideas for your DM to legalize your intended outcome:

1. Rule that it is possible to use magical effects outside spells. While spells do what they do, you can use non-spell magical effects.
2. Modify all spells to allow the caster to control the damage.
3. Give a feat or ability that allows the caster to control the effect of the spell, for free.
4. In doing what you intend to do, you invent a new spell. It is not a cantrip yet (you can't reliably replicate it), or it is a cantrip but does not count against your normal cantrip limit.

Most DMs I've met usually don't bother too much and let you do it anyway, but some might prefer to run spells as written. If they hesitate to allow it because they can't find a rule that allows you to tone the effect down, you can mention those ideas.

Answer 2

A Wizard who has chosen School of Evocation has the Sculpt Spells ability which grants the ability to reduce the effects of their evocation spells on selected targets by granting them an automatic pass on their saving throw. Since this is a specifically listed special ability for wizards of that school, and even it does not reduce the damage as much as you are asking for, the ability to control magic with the precision you are asking about seems unlikely.

My first thought on reading this question was that the Prestidigitation cantrip was a better fit for the end goal with the goblin but I was thinking of maybe making their clothes catch fire then go out. I completely forgot about the first listed effect of that cantrip, which is "to create an instantaneous, harmless sensory effect" and that is exactly what the non-damaging electric shock you asked about would be.

So no, a wizard cannot reduce the damage of a spell like shocking grasp. But there is a different cantrip that is perfectly suited to what your wizard hopes to accomplish so long as they have it available.