PROFICIENCY

Proficiency, susceptibility, casting cost, success rate, and efficiency
affect specific spells or skills. Unlike the INFLUENCE stat, these
modifiers can affect more than just a spell or skill's damage.

Proficiency affects the damage and healing done by the wearer with that
skill or stat. Like INFLUENCE the amount of damage and healing
modification is based on the skill or spell's base damage and healing. For
spells with debuff affects only, it also affects the opponent's chance to
fail any saving throw made against that spell (if applicable). For this
stat, a positive modifier is good for the wearer and bad for the wearer's
opponent. A negative modifier is bad for the wearer and good for the
wearer's opponent.

Susceptibility affects the damage received by the wearer against that
skill or stat. Like INFLUENCE the amount of damage modification is based
on the skill or spell's base damage. For spells with debuff affects only,
it also affects the wearer's chance to fail any saving throws made against
that spell (if applicable). For this stat, a negative modifier is good for
the wearer and bad for the wearer's opponent. A positive modifier is bad
for the wearer and good for the wearer's opponent.

Casting cost is the mana it takes for the wearer to cast that spell. This
stat has no affect on non-spell skills. For this stat, a positive modifier
is bad and a negative modifier is good.

Success rate affects the wearer's chance to succeed with that spell or
skill. For spells, this affects the wearer's chance to avoid fumbling when
casting that spell. For skills, this affects the wearer's chance to affect
their opponent with that skill, or avoid failing when using that skill, as
applicable. For example:
 - MEDITATE success affects the wearer's chance to successfully
          meditate and recover hitpoints.
 - PARRY success affects the wearer's chance to successfully parry
          an opponent's attack.
 - KICK success affects the wearer's chance to successfully hit
          their opponent with the kick skill.

Efficiency affects the combat lag associated with using that particular
spell or skill. The amount of modified lag is based on the skill or
spell's base combat lag. A positive modifier is good for the wearer and a
negative modifier is bad for the wearer.

In the future, each spell or skill will list more details about the
effects of these stats in their respective help files.