Greetings…
So, we have a situation where your enemy combatant, namely a spellcaster, has suggested that your comrades are doppelgangers who are planning on betraying the victim of the spell.
Now, I agree that suggesting that your comrades are traitorous doppelgangers, and that the character should kill them first is TWO suggestions. Not just a ‘justification’ and a ‘suggestion’. First it suggests to you to change your perception, and accept that your comrades are evil doppelgangers. Then there is the suggestion of action that you should attack them.
Well, just like others stated, the spell doesn’t make you stupid. You know that it’s going to be ‘harmful’ if you attack your ‘evil’ friends.
However, saying something leading such as, “I am not your enemy, they are!” or ”You’re friends are really evil doppelgangers!” is rather open ended. Leaving the course of action to the player as to what they should do knowing that their comrades are now their enemy.
With the suggestion “It’s a pool of refreshing water, go for a swim!” Again, I would argue it is two suggestions, unless the target is uncertain as to the contents of the pool, or somehow led to believe that it’s water. This would be pretty hard to do unless the target has a problem with their sense of smell.
Of course anyone is going to argue that anything that someone suggests is going to be unreasonable, if it’s going to negatively affect the character.
Evil Mage casts Suggestion, “Now is a good time to flee!” shouts at Wayne.
Wayne, “Oh, I can’t flee, that would be unreasonable of me to do that! To leave my friends and comrades behind! That’s just crazy!”
It’s a mind affecting spell. The purpose of the spell is to influence the actions of the target by suggesting a course of activity. But with the RAW here, if you don’t suggest a course of action, then the spell’s requirements aren’t met, and your spellcaster just wasted a spell.
If it’s a feasible and plausible suggestion, then there can be no argument about the situation. Now, of course trying to convince someone to do some harmful act by telling them it’s not harmful… “Oh, you can make that jump.” – Well, that becomes a tricky situation. If I were so inclinded as to rule that the spell changes the perceptions of the victim, personally, I would suggest an INT check against some difficulty, so that the character has a chance to notice the momentary lapse of reason.
But, what if your character is being told something like: “You can fly! – Jump, you can make it!” The RAW doesn’t say anything about changing the perceptions of the target. After all, the activity isn’t reasonable. What evidence does the victim have that they can fly? Or that they can make the jump? None. The spell doesn’t say that it alters the perception of the target so that they imagine that a pool of acid is water. Or that the space between two towers is a reasonable distance to be able to jump across. Or that you perceive your friends as doppelgangers.
I would have to say, without evidence to help support the spellcaster, such as an illusion or something else, the spell isn’t mind-altering enough to make the person perceive things that just aren’t there to begin with. Or I would give the target a circumstance bonus to save. Also, the spell description says that the spell is ineffective if they are requested to do something harmful. Harmful, for whom? The target themselves? Their intended victims? To a complete stranger? Again, another hole for the rule-lawyers to ride their donkeys through.
Who is the arbitrator of what is feasible and plausible? The distinction between "mostly" and "very" and "somewhat" reasonable is of course up to the GM. Certainly not the players. Because of course the players are biased towards themselves. Hopefully, the GM/DM is not biased. But then, if the GM starts throwing NPCs at the players telling them to “count the grains of sand on this beach” or “it’s a reasonable distance to jump across, go ahead… jump!”, then I’m going to start using the spell with just as much effect and power that the DM attributes to it.
Machiavelli, but you assessment is incorrect. The intent of the spell cannot be harmful. The spell, RAW, states that the spell will fail if the action is obviously harmful. An obviously harmful act automatically negates the effect of the spell... It’s a slippery slope to start comparing spells of the same level against one another, and asking yourself ‘is this as powerful as blah?’… especially with this wacky Vancian/D&D system.
However, if they do give the example that you can preface the action with a plausible rational, this implies that it does change the perceptions of the intended victim. So, with careful wording, the sky’s the limit! ”The sky is falling, flee for your lives!”
Fieari casts Suggestion, “We have just cast a spell on you and your friends that would shunt you elsewhere and replace you with a doppleganger, but you and only you have succeeded in resisting this spell. The spell will return your friends as soon as you kill the dopplegangers, so kill them.”
Imagicka resists, “Your sentence is run-on. I reject it outright because of the bad grammar!”