How would you model a spell made to grant a supernatural power?

[Ghsdkgb]

Like, what would the difficulty be to give someone Inhuman Strength or Speed or even Claws? Considering Aristedes could do it for himself, I'd imagine it'd be something under Evocation, perhaps a specialized class of it?

Also, would it vary based on whether you're casting it on yourself or someone else, as well as whether the recipient wants it or not?

[Taskill_Mckennan]

Are you doing this for a PC or an NPC and are they a mortal spell caster or other wise? Because if i have this infor it'll make it a little easier to craft

[Vargo Teras]

The basic idea I've seen is that it should take two shifts per point of refresh, but that transformative magic always has consequences, which should be equal to the effect.  So Inhuman Speed would run eight shifts; four to create a two-refresh power, four to create the mild physical consequence of Strained Tendons or similar.  Of course, if this is something that you do to yourself frequently, you can just take it as a power: Inhuman Speed with the Human Form limiter should cover something that you need to spend a supplemental action and a single point of mental stress to trigger via rote.

[computerking]

This is the part where Sancta posts a link to the Custom Power "Magical Self-Enhancement", that mimics Aristedes' ability, and allows it to be done with Evocation.

But in relation to Thaumaturgy, you should look up the Transformation conversations, and specifically the thread where Sinker asks "The Big Boss Man"(ie Fred Hicks) about transformation shifts required.

I believe adding a power with Thaumaturgy would require at least :

(Target's Resisting Skill) + 5 + (Refresh cost of power) + (Duration chart increase shifts) 

In shifts of power. And this is for temporary access to a power, costing the refresh cost in Fate points to use it for a scene.

Some Tables may say that you can't go beyond a certain duration before you have to spend refresh on the power and make it permanent.

[Sanctaphrax]

I guess I'm predictable.

This won't satisfy your desire for self-destruction, though, unless you intentionally take oodles of backlash.

I suppose you could pair this with another custom power to get that effect. You'll probably have to make it yourself, though. And then you might as well make an entirely new power.

But for whatever it's worth, here's an untested and probably unbalanced power from the master list that sort of approximates damaging yourself with magical enhancement.

PAINFUL TRANSFORMATION [+1]
Description: Shifting forms is extremely painful.
Musts: A Shapeshifting ability.
Skills Affected: Endurance
Effects:
Painful Transformation. Choose one form you have access to. Whenever you shift forms, unless it is into the chosen form, you immediately receive a Mild Physical Consequence related to the stress of transformation.

[Harboe]

I guess I'm predictable.

I like that power. Unfortunately, [Power] + Human Form seems a lot simpler and cleaner.

But for whatever it's worth, here's an untested and probably unbalanced power from the master list that sort of approximates damaging yourself with magical enhancement.

PAINFUL TRANSFORMATION [+1]
Description: Shifting forms is extremely painful.
Musts: A Shapeshifting ability.
Skills Affected: Endurance
Effects:
Painful Transformation. Choose one form you have access to. Whenever you shift forms, unless it is into the chosen form, you immediately receive a Mild Physical Consequence related to the stress of transformation.

I think this is a bad, bad, bad idea.

My premises for saying so:

• Most shapeshifters use their abilities to assume a "combat form," where they have better defense and/or offense.
• In DFRPG, one big attack is better than several weak ones (assuming equal opportunity to satisfy The Catch)

With that power, I get to boost my Fists and Endurance to Superb (assuming max skill cap), which grants me an additional mild consequence. I immediately use that slot to inflict the Fuelled by Pain and Fury aspect on myself and invoke it on my first attack.
Sure, the consequence can be used against you too, but this (as far as my 30 second look-over could tell) is a bad idea for a power. Maybe an aspect?

[Becq]

It seems to me that as long as you rule that (a) the consequence must be marked off before the transformation (so that it remains after transforming back, and for (at least) a scene after, and that (b) the free tag on the consequence is 'owned' by the player's opponents, then its not too bad.  Sure, the player can still invoke the aspect with a Fate point, but the hostile free tag would outweigh that.

[InFerrumVeritas]

Enough shifts to take yourself out (without consequences, since you're willing): 3-5 shifts.
2 shifts per refresh costed.
1 Fate Point per refresh costed as per the temporary power rules.