Each point increases the odds your having a 'critical'
success with your spell. A critical adds 15 spell damage to an spells
power.
Spell crit begins at 0.
Spell crit increases by 1 point for every 4 points of mind over 60.
Spell crit increases by 1 point for every 8 points of perception over 60.
Spell crit increases by 1 point for every 8 points of spirit over 60.