Would a charmed creature be considered Surprised when attacked?

Question

One of my players, an assassin rogue recently took the Fey Touched feat and used it to learn Charm Person. In our last combat, they used it to successfully charm an enemy in the middle of the fight, asked the rest of the party not to attack them, tranquilly walked up to them, and then attacked.

So Charm Person says this:

If it fails the saving throw, it is charmed by you until the spell ends or until you or your companions do anything harmful to it. The charmed creature regards you as a friendly acquaintance.

And since they're an assassin, they got this feature:

You have advantage on attack rolls against any creature that hasn't taken a turn in the combat yet. In addition, any hit you score against a creature that is surprised is a critical hit.

So my player considered that, since the spell made the target friendly to them, they shouldn't expect an attack coming and, thus, should be considered surprised for the purpose of that attack only, which would grant them a critical hit (with Sneak Attack because the fighter was in melee).

I'm a bit conflicted. I allowed it for this time, but even with the advantage to the saving throw due to the combat situation, I'm afraid it could become easy to abuse, especially with an enchanter in the party. RAW, I'm pretty sure that being surprised only count for the first round of combat and that a charmed creature is still aware they are in a combat situation, even if they can't attack the charmer.

Should I continue to allow them to do this going on, or should I tell them that it was a one time fluke and eventually allow them to take another spell with Fey Touched?

Answer 1

Not in Combat

The title of your question and the body of your question ask two different things. For the body, where you describe a combat situation, this would not work.

Surprise can happen only at the beginning of combat. The rules under Combat Step by Step (PHB, p. 189) say:

1. Determine surprise. (...)
2. Establish positions. (...)
3. Roll initiative. (...)

(...) Any character or monster that doesn’t notice a threat is surprised

so, surprise can only be determined before intiative is rolled. When you cast charm person in combat, the opportunity for surprise has already passed, and the victim cannot be surprised any more.

How you should rule, only you can decide. Given that this is clearly against the rules, and in addition is an exploitable tactic for an assassin rogue that can easily lead to one-shot kills, I personally would not allow this on a repeat basis.

Outside of combat

The title of your question also covers situations outside of combat. In such situations, this tactic could work. While the surprise rules in the PHB talk only about Stealth and Perception, there is a Sage Advice Compendium entry that clarifies what is meant by noticing a threat:

you must be caught off guard, usually because you failed to notice foes being stealthy or you were startled by an enemy with a special ability, such as the gelatinous cube’s Transparent trait, that makes it exceptionally surprising.

Usually means, not only. You would not expect a friendly acquaintance to suddenly pull out a weapon or use a weapon they happen to be holding to attack you, and if you were not already in combat, you could be caught of guard by such an action.

When combat starts or ends is also not that clearly defined, so if you cast charm person on a creature before combat, which can be considered a hostile act, the DM may have you roll initative right then, before letting it resolve. It then will be to late for a surprise attack the following round (it could work if you have action surge, or are under haste to get another Attack action that same initial round). But, if there is no group of opponents to respond to this, you might be able to just wait for a bit until you are out of combat again, and then surprisingly attack.

This can help if the creature you are trying to cast charm person is weary of you, and normally would suspect that you could pull out a weapon any time to attack it. With an entirely unsuspecing counterpart, you would not even need to cast charm person to surprise them, because they already would be caught of guard by such an action.

Answer 2

Surprise is only for the first turn of combat.

The rules for surprise state:

The DM determines who might be surprised. If neither side tries to be stealthy, they automatically notice each other. Otherwise, the DM compares the Dexterity (Stealth) checks of anyone hiding with the passive Wisdom (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.

If you’re surprised, you can’t move or take an action on your first turn of the combat, and you can’t take a reaction until that turn ends. A member of a group can be surprised even if the other members aren’t.

Surprise is determined before initiative is rolled*. Determining surprise is the very first thing the DM does when an encounter begins, and it applies only to the first turn a creature is in combat. So no, the rules do not give the charmed target the surprised condition.

However, this seems like a good time for the DM to give advantage on the attack, as the rules for Advantage and Disadvantage state:

The DM can also decide that circumstances influence a roll in one direction or the other and grant advantage or impose disadvantage as a result.

Answer 3

A charmed enemy doesn't become a stupid enemy

If a friendly acquaintance came towards me with weapons drawn and I knew that there was some potential reason that said acquaintance might want to cause me harm I would be on guard. As soon as I became on guard I would no longer qualify for the surprised condition.

I might still act friendly with that acquaintance, but would still be cautious, and the fact it is magical doesn't change that.

The target doesn't forget what happened prior to the charm, they just treat them differently for a short period, but won't lose sight of the fact that this person is / was an enemy.

Think X-Men, Charles knows Erik is a friendly acquaintance, sometimes, but is still usually on guard when he is around because he knows that their values don't align. Charm spells do that.

Now if you just charmed a random guard who didn't know you from Adam, then sure this would work, but if that is the case you do likely wouldn't have had to roll initiative in the first place, because the charm wasn't in combat.

Answer 4

The DM can allow this, but it is outside the rules

Nothing about being charmed mentions anything advantageous to the charmer in combat. You might be my friend, but when you pull out a rapier and thrust it at me, I notice. No surprise, no advantage, nothing for combat (except not being attacked by the charmed creature). Charm Person is for social encounters. While we're at it, a person who passes a Charm Person save will likely alert the Guard at best and attack you immediately at worst.

To dig in, let's look at the Charmed Condition:

A charmed creature can’t attack the charmer or target the charmer with harmful abilities or magical effects.

The charmer has advantage on any ability check to interact socially with the creature.

Nothing here about attacking the charmed creature or Surprise if you do so.

Surprise really requires stealth to work, and my experience is that parties get surprise a lot less often than they in general, and Rogue Assassins in particular, would like. It's fine you allowed this once as a "rule of cool," but that doesn't mean it needs to continue. Players are free to try to come up with creative combos, but this one is really outside the lines.

Answer 5

This would be homebrew. As already mentioned, the rules don't allow surprise after the first round of combat, BUT....

Personally, I'd let the guy have his fun. Let him attack the guy and potentially kill him. But now, now he's known for killing his allies. And before he says anything like, "the party wouldn't tell," I promise you, word gets out. Someone's gonna be in their cups one evening and they're gonna spill the beans about "not getting on his bad side because he'll straight up kill you," or something. It doesn't matter how, but at some point if it's being abused, the word got out and now everyone knows.

Another option is to basically do the above, but instead of giving him one and essentially barring it for the rest of the game, turn it into a mechanic by giving him a bluff/sleight of hand check against the charmed target's insight (and this lets you weigh it one way or the other if it seems like it's being abused or if it's too tough).

On top of that, you could also potentially add extra "safety checks" to the charmed target. When I run games, I handle charmed people as "not stupid." They're not going to go stand on the edge of a cliff because you charmed them and, "Wow now that we're friends that cliff DOES look really cool...." They're just not your enemy anymore. If someone's standing behind them, holding a knife to their back and grinning maliciously.... Probably gonna be able to pass that check and defend themselves.