Regarding Charm and Its Varying Iterations in D&D
Given that Charm has found its way as a focal point for discussion, I figured I would break out its functionality in varying rulesets and what, if anything, it can contribute to this discussion. First, I'm going to canvass 3.x Charm and I'm going to include a quote from a thread sometime ago where @
N'raac and myself were discussing its usage as a constraint on spellcasters. We were also discussing the pervasiveness of Arcana/Spellcraft acumen by the elite and layfolk (as we have elsewhere including this thread) as it is applicable to the adjudication.
Originally Posted by
Manbearcat 
A couple of things here. I've never ruled (in any edition) that the target of a successful Charm spell understands that they were under the effects of a mental compulsion for the duration of the spell. Only in scenarios of extreme outliers (such as if the player tries to get the NPC to do something specifically antagonistic toward its own nature...or if the NPC is a well accomplished spellcaster) would I consider this ruling.
My understanding is that the rulebooks agree with that approach. I can't find it right quick in my old books but I know the 3.x books find it this way on PHB p177:
"Succeeding on a Saving Throw: A creature that successfully saves against a spell that has no obvious physical effects feels a hostile force or a tingle, but cannot deduce the exact nature of the attack. For example, if you secretly cast charm person on a creature and its saving throw succeeds, it knows that someone used magic against it, but it can’t tell what you were trying to do. Likewise, if a creature’s saving throw succeeds against a targeted spell, such as charm person, you sense that the spell has failed. You do not sense when creatures succeed on saves against effect and area spells"
It provides ruling guidance for successful saves only and is silent on failed saves;
I still remain unconvinced that the 3.x ruleset provides guidance and/or support for GMs to unilaterally impose punitive results, post-usage, to the player who deployed it (thus turning it into a "nuclear option" as @
pemerton put it). The spell specifically doesn't lead you to this adjudication nor does any advice I have seen. I have never used it as such. Use charm versus someone, or in the presence of someone, with Knowledge Arcana or Spellcraft ranks? Yes, a check should certainly be made to determine if Charm was deployed. This does, of course, presuppose that the GM has world built to levels of extremely fine resolution; that most, all, bit-player and minor NPCs have their knowledge skills statted and that every situation/locale is pre-ordained to have a party with Knowledge Arcana or Spellcraft present. Conversely, you can work off the presupposition that all castes have 1 rank of the relevant skills and get a check to determine if they have any concept of "Charm" spells. Both of those, conceptually, are "A Bridge Too Far" for myself.
D&D 3.x
Resolution: Save vs Will. Bonus to saving throw if being threatened. Orders = opposed Charisma check.
Effect: Attain friendly/trusted ally status.
Classic Usage: Pacification in combat or in social conflict; parlay, information gathering, or social wheel-greasing.
Target recognition of enchantment: Nothing in spell description nor anything specifically called out in GMing advice. As noted above, if your world presupposes that either (i) every person in the world has ranks in Knowledge Arcana/Spellcraft or (ii) there is always someone at the relevant locale that has Knowledge Arcana/Spellcraft, then it is
reasonable to mechanically resolve the "Charm Awareness" as an NPC skill roll.
D&D 4e (multiple iterations)
Resolution: Sub Arcana for Bluff and/or Diplomacy on a singular effort to persuade.
Effect: Successful task resolution or gain a success in a Social Skill Challenge. Attain friendly/trusted ally
status for the resolution of this panel/situation/scene.
Classic Usage: Social conflict task resolution or Skill Challenge; parlay, information gathering, or social wheel-greasing.
Target recognition of enchantment: Nothing in spell description nor anything specifically called out in advice.
13th Age
Resolution: Charisma + Level vs Mental Defense. If attacked or ordered to attack, target gains save each each turn.
Effect: Out of combat pacification. You are now friends for good unless you behave hostile toward them.
Classic Usage: Pacification in combat or in social conflict; parlay, information gathering, or social wheel-greasing.
Target recognition of enchantment: Mechanically defined; if you miss by 4 + or roll a natural 1, the target, and his buddies, are aware of the Charm effort and hostility should be the expected response.
Dungeon World
Resolution: The charm effect is guaranteed (player fiat) but there may be complications that the player gets to choose. Roll 2d6 + Int (same for any spell). On 10 + you cast the spell and retain it for later use. On 7-9 the spell is cast but choose one:
* You draw unwelcome attention or put yourself in a spot. The GM will tell you how (THIS could very well be the "target is aware of charm effort" complicaton...or it could be something more interesting)
* The spell disturbs the fabric of reality as it is cast; take - 1 ongoing to cast spells until the next time you Prepare Spells.
* After it is cast, the spell is forgotten. You cannot cast the spell again until you Prepare Spells.
Effect: Out of combat pacification. You are now friends for good unless you behave hostile toward them.
Classic Usage: Pacification in combat or in social conflict; parlay, information gathering, or social wheel-greasing.
Target recognition of enchantment: Nothing in spell description nor anything specifically called out in advice.
Of note; all of these rules systems offer a mundane analog for quelling hostilities/parlay facilitation/social conflict grease/adjusting NPC reaction.
