Fear is a Warlock spell in the Affliction tree. Fear causes a single enemy to flee in terror, disabling it for a short period of time. This can be a powerful tool to warlock crowd control, although care must be exercised when using it.
When a victim is feared, they are granted extra chances to break the spell when they take damage. Spells that cause no damage do not break fear.
Repeated castings of fear increase the victim's ability to resist it for players (due to the Diminishing Returns Rule), but not for mobs, who can be feared indefinitely.