Dread Curse: Willpower is a Destruction spell available in The Elder Scrolls III: Morrowind that lowers the value of a victim's willpower. Attribute does not return to its original value at the end of the spell's duration; they can only be restored with the appropriate Restore Attribute spell or potion.
This spell is not available for purchase in Morrowind or expansion packs. Although not intended for use by the Nerevarine, it can be acquired on the PC by using the console:
Player -> AddSpell "dread curse: willpower"