Anyway, why sponsored magic?
Because sponsored magic seems to be the cacth all term for any kind fo magic that draws power above or beyond the "base", Kemlerian necromancy, and ley lines are both forms of sponsored magic.
Who/what is sponsoring it?
As the precedent of kemlerian necromancy shows us sponsored magic isn't always about it actually being sponsored, its just magic that draws its power in a different or external way.
What's the source of the power?
As i attempted to express in the write up "this power is much more then the occasional use of temporary pain or anger to fuel your magic, it is a complex and comprehensive understanding of how to use emotions, pain, suffering, and sacrifice." In the same way that kemleran necromancy pulls directly on the power of death and "the darkness between the stars"
Sadicas pulls directly from the power of agaony and suffering.
Where do the debts "go" and who/what calls them in?
Same way/place with kemlarien necromancy and ley lines, it doesn't go to any specific being they exist as a form of "taint" on the user that is just a natural response from powering your magic wit agony. as i explained in the write up "While there is no sentient force corrupting you all uses of magic require the magician to believe that that spell is Right, channeling pain in such a way leaves a mark on your soul forever changing who and what you are. "
Simply put, what's wrong with "TROUBLE: My painful, debilitating disease" - why create an entire 'field' of magic when one always present aspect will do the trick?
Several reasons, one having it as a trouble could certainly be a gold mine of fate points,
if your story teller wants it to be, And it dose represent the pain you'd be in, but to invoke it you'd have to actually have fate points to tag it, and that seems far to hit and miss for me. Theirs definitely nothing stopping someone from taking it as a trouble and or an aspect and playing that way, the method works, for given variables of work, but
to me it doesn't work well enough to represent the consistent nature that these kinds of conditions are. [ i myself have fibromyalgia and i wish it only came up as infrequently as " whenever the st feels like invoking it" Essentially its just not "always present" enough for what im looking for.
Secondly to get a consistent bonus we need to pay refresh for it, i don't have a problem with that so we then have to look at how we want to represent it. We could just take a variation of refinement that only applies in specific ways. but conceptionally that's the same thing as kemlarian necromancy so presumably that's the appropriate mechanic to use. Logically using this kind of magic should have a profound affect on a person and would be available to anyone that wanted to and knows how to draw power from pain, thus
Sadicas as a flavor of sponsored magic, that taints you the more you use it, and a minor variation of it for those who draw pain from them selves instead of from torturing others.
Thirdly i don't really view this as creating a new field of magic, i view it as making numerical rules for something that should probably exist in the setting by using the precedents and mechanics available in the system