How does one handle spells out of combat?

Question

How would you handle a player casting, for example, Charm Person on a high-level wizard out of combat? It has V, S components and my thought is that the wizard, who would be knowledgeable about magic, should get a chance to interrupt the spell. Or would the start of casting the spell result in a combat timescale with inits rolled, making the wizard have a chance to ready?

This just happened during the last session, and I didn’t let the wizard have a chance to interrupt, resulting in her spilling some pretty important secrets after a failed save. It felt a bit off as the level difference was big between the caster and the target.

Answer 1

It would hinge on the wizard being surprised

The idea of the wizard being taken aback by an action and not having a chance to react has a mechanical representation in the rules, it's called the surprised state and is part of the initiative rules, but let's cover a few things first.

Firstly, while not explicitly covered either way in the rules, you can take actions (and bonus actions and reactions) out of combat. See What actions/bonus actions/reactions can a character perform out of combat? and Can a Bonus Action be used outside of a combat encounter? for more on the topic. The combat rules, or initiative specifically, are a tool the DM can use when many things start happening all at once (eg. combat).

So, without rolling initiative, all the wizard's conditions for casting counterspell should be met (a creature they can see can be seen casting a spell). If you do roll initiative though, the wizard would still be able to use its reaction unless it was surprised and its turn is after the PC's. Whether it is surprised is wholly up to the DM, but personally I would land on them seeing the PC do this making them not surprised. If they are surprised they would be able to take the reaction to cast counterspell once they'd had their turn (they wouldn't have been able to do anything on that turn).

However, having everyone roll initiative shouldn't be necessary unless the wizard (or any other PCs or NPCs) would follow up on the spell casting (retributive fireball?). Instead, if you're just rolling initiate for one interaction for two participants, do what I do and simplify it to a Dexterity ability check contest. This might be a good tool also for cases like this where the later outcome is heavily depended on the first action. (There would presumably not be any combat if the wizard becomes charmed and I find some players rather jump to conclusions, and swordpoints, once you tell them to roll initiate and that stings for the player who were trying to charm).

Answer 2

Initiating a hostile action triggers combat

"Combat" is not defined in the rules so it takes its normal definition: "a fight or contest between individuals or groups."

Once the player declared an intention to cast Charm Person, combat is initiated and the normal rules apply:

COMBAT STEP-BY-STEP

1. Determine surprise. The DM determines whether anyone involved in the combat encounter is surprised.
2. Establish positions. The DM decides where all the characters and monsters are located. Given the adventurers' marching order or their stated positions in the room or other location, the DM figures out where the adversaries are--how far away and in what direction.
3. Roll initiative. Everyone involved in the combat encounter rolls initiative, determining the order of combatants' turns.
4. Take turns. Each participant in the battle takes a turn in initiative order.
5. Begin the next round. When everyone involved in the combat has had a turn, the round ends. Repeat step 4 until the fighting stops.

The general consensus is that no one is Surprised (see Should players get a surprise attack by interrupting a villain's speech?). I, personally, take the minority view and that a surreptitious attack from a known creature can cause surprise - but you do you.

If your high-level wizard is not surprised when the Charm Person is cast they have their reaction available (either because they aren't surprised at all or were surprised but rolled higher initiative) and can use Counterspell, for example. On their turn (which can be before or after the Charm Person) they can act normally if not surprised and can, for example, use Meteor Swarm - "Do not meddle in the affairs of wizards, for they are [NOT] subtle and quick to anger.”

Answer 3

Casting a spell still takes an action, even outside of combat.

If the Wizard NPC could see the casting they were free to use their reaction to cast Counterspell, if they had it available.

A reaction is normally only relevant in combat but the description says:

Certain Special Abilities, Spells, and situations allow you to take a Special action called a Reaction. A Reaction is an instant response to a trigger of some kind, which can occur on Your Turn or on someone else’s. The opportunity Attack is the most Common type of Reaction.

Without using a a reaction, you could rule that the players then slipped into a combat like initiative order but I, personally, would rule that the initial action, casting Charm Person, happened before anything else regardless of initiative order, like a surprise round.

Answer 4

There is no such thing as casting a spell on an opponent 'out of combat' doing such a thing automatically initiates combat as any spell cast against an unwilling target immediately is an hostile move and thus the NPC mus react to that threat.. encounter starts... If the opponent is unaware of the whole party he might be surprised but it is very likely he will not at least see or detect one of the party members if they are interacting with him so he is aware of the party and cannot be surprised. (to be surprised he must be unaware of ALL members of the opposing party)

Supporting rule :

PHB p182, encountering creature. & Suprise rule

Encountering Creatures. If the DM determines that the adventurers encounter other creatures while they’re traveling, it’s up to both groups to decide what happens next. Either group might decide to attack, initiate a conversation, run away, or wait to see what the other group does. Surprising Foes. If the adventurers encounter a hostile creature or group, the DM determines whether the adventurers or their foes might be surprised when com bat erupts. S ee chapter 9 for m ore about surprise.

PHB p189 order of combat

The DM determ ines w ho might be surprised. If neither side tries to be stealthy, they automatically notice each other. Otherwise, the DM com pares the Dexterity (Stealth) checks of anyone hiding with the passive W isdom (Perception) score of each creature on the opposing side. Any character or monster that doesn’t notice a threat is surprised at the start of the encounter.

Initiative determines the order of turns during combat. W hen com bat starts, every participant m akes a Dexterity check to determine their place in the initiative order.

CONCLUSION: As you can see AS SOON as the start of combat erupts, an initiative roll and surprise effect must be made. Casting a spell on a unwilling target is a threat and actually an attack against that unwilling target. combat starts.

Also surprise effect if negated if someone notices "A" threat not "ALL" threat. So if the target notices at least one of the opposing party members (and knows this creature is part of the opposing party attacking him right now he is detecting A threat and thus is not surprised.