Sponsored magic allows a character with it to potentially cast Thaumaturgy with the speed of Evocation, depending on the nature of the Sponsor and type of effect the Thaumaturgy would have.
As an example of Sponsored Magic from YS, Kemmlerian Necromancy allows a character with it to cast Necromantic or Neuromancy/Psychomancy ritual spells with the speed of Evocation. This form of sponsored magic in particular can get 'interesting' since a caster could let loose with a 5 shift mental attack, which would not be hindered by most standard block spells and on a successful hit would basically force either a taken out effect, or a character to start taking consequences. Not to mention adding to the mental stress track which would negatively impact an enemy caster. Not that I would ever write a one-shot con game where players would encounter this...
Actually, for something like a Sunlight spell, Seelie Magic would be an appropriate Sponsor in my opinion, being associated with light, warmth and growth.
Remember, Sponsored Magic is basically a theme of magic where an outside element/power/something augments the magic, as long as it is appropriate thematically with whoever/whatever the Sponsor is. If you want to have some things start to get really wild, have someone with site specific Sponsored magic from a
genus loci.
-Cheers
