I got thinking about magic today, and thought I'd consider what it would take to make one character "fall irretrievably in love" with another.
Never mind that it breaks one of the practical laws of magic (don't fuck with people's hearts & minds). You
know people do this kind of magic all the time!
In Fate Core, you want to impress someone, you'd roll 4dF + Rapport hoping to overcome their Empathy resistance. This still applies. magic simply allows a way to supercharge that Rapport roll.
With magic, you have the option of building up magical power to make that thing happen.
So, mechanically, how much power do you need to raise?
If an average person has a five-point Will stress-track, you must overcome five shifts to force that person to take a Mild(+2) Consequence.
+04 Max Potential 4dF roll
+04 Max potential Empathy rank
+05 Max potential Will Stress-Track
+01 to make it happen
=====================
+14 shifts of power
You can't leave-off half-way through and do it again later, unless you're willing to bank the raised power into some sort of talisman as a temporary storage device. And that comes with all sorts of risks.
Of course, you can also do a lot of leg-work and set up a whole bunch of Advantages to add to the spell-effect. I mean, ultimately, that's precisely what you're doing with the ritual spell in the first place: You're creating a huge pool of Advantages to blow on one Rapport roll...
So, what we've got here now is the successful application of a Mild(+2) Consequence. Maybe that's enough. Maybe all you need is for the target to be predisposed to like you for a scene or two.
But remember! People recover from their consequences!
So, if you want to make a
Permanent change to their feelings for you, you need to generate this much power:
+04 Max Potential 4dF roll
+04 Max potential Empathy rank
+09 Max potential Will Stress-Track
+02 Minor Consequence - (cleared after a thread/scene once recovery begins)
+04 Moderate Consequence - (cleared after a chapter/session once recovery begins)
+06 Severe Consequence - (cleared after a milestone/scenario once recovery begins)
+01 to make it happen
=================
+30 shifts of magic to make that guy love you--and make it stick!
It would probably require them to change on of their Character Aspects.
This level guarantees an emotional change that will last. Well, almost. There's no telling how many existing Advantages they might have to call upon themselves to resist your Rapport roll...
Now, if you've only got a Fair(+2) Lore, it's going to take you a fair bit of time to generate 30-shifts of power.
I have to Roll all that?
Hell, no.
I'm not even remotely not interested in roleplaying this or even dice-rolling it. It's just not that dramatic.
So, what's to prevent a player from saying
"Well, I've been setting this up for weeks, so I've amassed three hundred shifts to apply to this..."?
Human Nature.
So, how do we determine how much power has been raised?
Discuss it with your GM.
To make this worthy of drama, there may be some roleplaying prerequisutes. You need a lock of her hair, you need to wait for a full-moon to perform the end-ritual, or perhaps you need a specially consecrated thing... Or maybe someone stole one of your power-receptacle talismans on the night of the end-ritual...
I'm way more interested in what you had to go through to get there than jus whether you got there or not...