The mind hovers closer to insanity than most people want to believe. A strong
psionicist can push a victim's mind just close enough to that border and show
them what madness really is. Crippled by sudden visions and impulses,
complicated actions, such as spells and skills, become much harder for the
struggling victim for a short time. Discipline and psychic resistance will
lower the effect of the spell, but even the undead are at least partially
vulnerable to the grip of insanity.
Mastery prolongs the effect, while knowledge of mental defense increases
the likelihood of interrupts.