Not sure if something like this has been done already, but I like the idea.
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Dressed by the Storm
Muto Corpus, level 55
R: Per, D: Conc, T: Ind
Req: Auram
Your body turns into lightning, while keeping a vaguely human form, for as long as you concentrate. While in this form, you're extremely hazardous. Anything that comes into contact with your body will be as if struck by lightning (+30 damage) and you're blindingly bright (Stamina stress roll of 9+ to avoid temporary blindness. Botching means permanent blindness). In fact, you're also blindingly fast, being able to relocate yourself instantly anywhere you can see in straight lines (Perception + Finesse stress roll of 9+ to "land" safely if trying to move further than about 50 paces. A botch means that you missed the intended destination, probably causing harm to yourself or your surroundings, and automatically failing to maintain the spell. A failed roll means disorientation - make a Concentration roll of 9+ to maintain the spell, with a botch meaning adverse effects like motion sickness). Any successful relocation will also produce a booming thunderclap (Same roll as for blindness, in this case to avoid deafness and/or being blown away by the shockwave).
While in this form, you aren't solid - actually, you aren't liquid, not even gaseous, however, lightning is too chaotic for delicate actions such as slithering through small openings (it would be like threading a needle in an earthquake). Of course, you can't really hold anything, being immaterial, immune to other sources of lightning, and there is the strange risk of conductivity. Coming into contact with enough metal or water will "discharge" your body, making it extremely difficult to keep your form (make a concentration roll of 15+ to maintain the spell. A botch means a very spectacular accident related to conductivity, like actually losing body mass, or finding parts of your body fused with metal objects or liquefied in a body of water). However, as long as you manage to maintain the spell while touching such things, you'll shock anything else in contact with them.
Finally, lightning is weightless (or so it seems), so you're not really bound by gravity, but the chaotic nature of this spell makes flight extremely dangerous... as extremely fast as it could be.
(Base 30, +1 Conc, +4 Auram effect wholly divorced from its normal context)
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So basically it's a spell that turns you into a living Incantation of Lightning. I tried to make it as flashy and chaotic as it sounds, without being too annoying or meticulous with the effects. Basically you become immaterial, explosively noisy and shiny, zap the hell of anything stupid enough to directly touch you, and you can "quasi-teleport" around, but touching anything conductive will break havoc with the spell (or let you zap a whole beach full of people). You can also fly, if you're reckless enough to risk losing control of the spell while in the stratosphere, or if you really are in a hell of a hurry.
Basically, this spell has room for VERY spectacular effects... Both good and bad. I wanted it to be a very appealing eye candy full of traps, and let Darwin sort'em out, lol.
I used the Creo Auram guidelines for very unnatural weather effects since I felt that turning into human-shaped lightning should be way harder than turning into mist.