We had an interesting scenario in our game last night where one of the magi, using an arcane connection and successfully overcoming another (NPC) magi's MR, cast Enslave the Mortal mind. After a brief interrogation, the magi then ordered the 'enslaved' magus to kill herself.
Since the spell description reads: "Enables you to completely control the loyalty, emotions, desires, interests, and activities of any person.", does this mean the target could really be ordered to take their own life? What exactly does 'activities' entail? The rego mentem guidelines do not appear to be very helpful in this case, but I might be missing something?
The spell employed uses the effect of the highest base level 30 (ArM5 p.151 box): "Completely control a person's mind and emotions." Unless the target has an Essential Personailty Trait (RoP:M p.54 Essential Traits) Carefree or such preventing suicide, the spell should work.
Enslave the Mortal Mind on a magus typically requires a lot of work to make it penetrate, though - and using it to compel suicide requires more work to prevent or misguide the subsequent Quaesitorial investigations. Look up HoH:TL p.70ff Quaesitorial Magic and HoH:TL p.64ff Endorsing Testimony for the means usually employed in them.
In the specific case of a magus, I might consider allowing a Familiar to use the True Friend virtue to overcome the effect of the spell - the text of that virtue does say "If any enchantment keeps you from your true [friend]'s side, the power of your devotion can probably break it", and "killing yourself" is a pretty ultimate case of being kept from their side. That depends on the familiar having the opportunity to react, though, and the magus having a familiar in the first place. Similarly, if they had a True Love/Friend from another source, they might be able to break the spell.
Ultimately, though, Enslave the Mortal Mind is a level 40 spell, the same level as the Perdo Corpus instakill "Clenching Grasp of the Crushed Heart". It's not unreasonable to be able to use it to kill someone (the spell is more flexible, true, but it's also slower).
I might sidestep issues of wording and ability to evade by making a simple com+finess roll against int+language to allow the suiciding magus to pervert the intent of something this dramatic... but even if they succeed the result should be bad ( for example- ordered to kill myself I drink a poison that will work in 24 hours after writing a suicide note that will be found well before this time and possibly include the phrase "I'm just not feeling myself"
In addition, if your mind is ever overcome by another force your familiar may be able to free you. To be successful, it must roll 9+ on a stress die with the silver cord score as its bonus (one attempt per day).
It seems to me that "Enslave the mortal mind" is a textbook example of what having your mind overcome by another force means.
I do think that ordering someone to commit suicide should be possible, though I would probably not allow it within my own group because I find the thought too disturbing to be comfortable story-guiding it.
You also have to consider how the magus in question chooses to commit suicide. I would think that unless a method of suicide is specified the magus themselves chooses how they will do it based on their sensibilities and expectations of how people go about such things. Yes they magus might drink poison if they have any lying about, but who does that? Having a deadly poison just lying about is hardly normal, even for magi.
It is quite possible that the NPC might not have any idea how to actually go about doing it. Say they might decide to jump from a window in their tower and get stuck in a small window or arrow slit failing to realize that they are not quite slender enough to squeeze through or jump through a window only to realize that a 10 meter drop is enough to get seriously hurt but nowhere enough to guarantee death, especially not for someone with a bronze cord and form bonuses.
I'd absolutely allow this. I wouldn't allow true friend to stop it except in the case of where that true friend is a familiar since killing yourself also kills your familiar and you should be able to use true friend to resist the influence to save your friend.
As interesting is how would you cover your tracks?
If you have total control of the magus, then a good way would be to have them go tell their sodalis that they intend to conduct an experiment in their labs and absolutely require no interruptions. That could maybe get you a season. I'd rather more though recommend using the same arcane connection to destroy the body afterwards using perdo corpus. Its not a high levels spell and you could get the magus (while still mind controlled) to undress and neatly pack their clothes, belongings, lab away so that it looks like they have gone away. By the time their sodalis think to check on him, months might have passed. By the time they get the quaesitors round, it could be seasons. There's no body, no signs of any violence. There'd be some decaying of the magical residue in that time too.
Most people in fact do have deadly poisons lying about, they just don't think about them that way. Check under your kitchen sink and see how many things are marked poison. Now a medieval peasant might not, but in a magus lab? Do they use mercury, or precious dyes? The latter might well contain arsenic... getting thee dosage right might be tricky- they might even try to kill themselves and flat out fail...
Or that even if he comes up with a plan, it just goes wrong, and he ends with a varying severity wound instead of death. According to Wikipedia only around one of each 25 suicide attempts ends in death.
So for me the “kill yourself” order is quite dramatic, but not much likely to be successful.
Of course there is also the question- even in modern terms, or intent: many suicide attempts are in fact trying to get attention rather than actually trying to die. Then there is he ever infamous "death by unga bunga" I won't repeat the joke here, but suffice it to say that a person simply ordered to kill themselves with no other parameters might well decide to drink themselves to death or take some other similarly pleasurable yet circuitous route to the great beyond.
Yeah, or given that usually life is a deadly experience (because, well, you end it always dying), a philosophical target, when ordered to die but lacking any time parameter, could chose to keep on with his life, and kill himself of old age. Not that I think that the spell discussed here would leave much room for that kind of freeing argument (and it shouldn't: if you take a 40 level spell and turn it into something pretty useless unless you craft your wordings carefully or have it not working most of the times, that character is going to be frustrated, thinking why on earth didn't he just made a CrAu specialist that could toast people with lightnings straight out of Gauntlet), but anyway if I were the caster I would be more specific. Something like commanding him to go to the top a hight tower and jump over its highest window (and then guiding him all the way down, just in case he sponts some levitation or something) (which maybe would be a good idea, if these spells were actually used to gain more speed on the way down! The trace of these spells could convince a Quaesitor that that was either a suicide or a nasty spell botch).