Just to throw it into the mix, here's another good passage from the RAW regarding magic and mental attacks, from the section on mental conflicts on YS217:
Being able to attack the mental stress track is no small feat. The kind of abuse necessary to inflict this kind of damage on another person usually takes a great deal of time and energy, the result of established relationships going horribly awry. Shortcuts exist—certain triggers in the character’s history might allow access to deeper recesses of the mind. Perhaps the most terrifying example of this is the mind magic available to wizards or the mental powers of other supernatural creatures. Even as total strangers, these people can instantly strike at the heart of what makes people who they are, forcing them to be temporary thralls to the creature’s will—or worse.
The wording here makes it clear (at least in my mind) that the design intends for mental attacks to be possible with magic. The use of "instantly" makes for a strong implication that this applies to Evocation, though it might be argued that this was intended to refer to Psychomancy via Sponsored Magic's "With Evocation’s Methods and Speed".
At this point I'll stop talking about what is and/or my interpretation thereof, and start talking about what should be, or at least my take on the subject:Mental attacks are dangerous, dangerous things. To both sides. They are not the DRFPG version of "Mana Bolt" from ShadowRun. You are not sending a mental punch directly into the target's brain, with the probable result of knocking them unconcious until they gather their thoughts.
No, what you are doing (at least with Evocation; Psychomancy and specialty mental attacks like Incite allow for a more finesse) is taking aim at a fragile network of beliefs that makes up who the target
is, then letting loose with a mental hammer. Loving Husband and Father? BAM! Thug, but loyal to his boss? BAM! Woman looking forward to getting home from work to spend some time with her nearly-grown kids? BAM!
When you shoot someone with a gun, your bullet might hit somewhere other than you intended, but the result is likely going to fall into the "hole in body, fluids leaking out, system shock" bucket. But with mental attacks, the results can be, quite literally
crazy. They won't necessarily be permanent; on YS219, it says regarding mental/social conflict: "The second thing to keep in mind is that no conflict results are really permanent, with the potential exception of an extreme consequence." But they should be quite dramatic when they happen.
So here would be my suggestions for Evocation-based mental attacks:
1) Think of mental conflict as a form of 'mini-game' taking place in the background of the physical conflict (or whatever the foreground scene is). It is not simply another damage type, it is a seperate conflict happening concurrently with the scene as a whole.
2) If the target is not badly overpowered mentally, make the normal rolls and come up with a resulting consequence that will make the remaining scene interesting. If need be, make up a random chart, or use Tarot cards or something for inspiration. Alternatively, you might make a consequence that twists and (temporarily) conflicts with one of the victims Aspects. Perhaps the loving husband mentioned above might have "My wife is my life" joined by the consequence "My wife is the bane of my life" until the consequence recovers. The results may or may not be immediately apparent...
3) If the target is badly overpowered, make use of the concession rules. The target has lost the mental conflict mini-game, and the GM (as the conceeding party) nominates the nature of the mental damage that has occured. Be colorful, and make the result ... interesting. Similar to #2, but potentially more extreme and/or longer-term, including potential changes to the character's aspects (though not with the permanency of an extreme consequence). Note that Being 'taken out' in this manner does NOT necessarily mean that he has lost the physical conflict. It might, for example, mean that the target gets shoved off the mental ledge known as 'sanity' and goes totally ape-shit berzerk -- which might change the course of the fight in an unpredictable way. Or it might mean they go into a coma, which would knock them out of the fight completely.
Remember that every use of this against a mortal is Lawbreaking, and should result in the attacker gaining the stunt and possibly suffering an aspect shift.
In addition, consider that the books and rules describe mental attacks as an invasion into the mind of the target, which can also expose the attacker to the mind of the target. It might be worth reflecting this by giving the attacker an aspect along the lines of "I've been in the mind of a _____" to reflect this experience. Have this aspect last for the scene, or the session, or until its used, as appropriate. Compel it to make the attack reel back from the horror he has exposed himself to, or suffer flashbacks, etc.
Just some ideas.
