Page YS289 in the sidebar labeled "The dark powers are always willing to help"
Sometimes the sponsored practitioner can
dig deep and draw more than a single invocation
from his sponsor on a single roll. This
can help pay any cost associated with casting a
spell, at the rate of 1 debt for every 2 shifts of
effect. So if you need to take a 4-stress mental
hit to cast a big evocation and can’t (or maybe
just don’t want to take the consequence you’d
have to), the sponsor will gladly take the hit
for you, in exchange for increasing your debt
by 2.
Some GMs might want to restrict the
amount of times this can be done during a
single scene or session, but on the other hand,
the dark powers are always willing to help...
So a spellcaster with sponsored magic can increase any spell by 2 shifts per debt they're willing to rack up (within the GM's tolerance of course).
There's also the ability to treat toughness powers as if they are one level lower (YS288) but that's a little more circumstantial.
