Rule of 15

-1 point

Prerequisite: At least one applicable skill at 16+.
The Rule of 16 (p. B349) applies a level sooner for one class of
resisted supernatural skills, such as Enthrallment skills, skills
acquired through Trained by a Master, or spells of one college.
You still roll against your full level, but are capped at 15 for the
purpose of overcoming resistance.