Than trying to run away from melee oathkeepers in the north downs. They are one of many mobs that cause dread when you are in close proximity. Whenever you first get the dread effect your screen flashes with a bright evil eye and a sound effect plays. However when trying to run away from oathkeepers you move in and out of this dread range constantly as they follow you, causing the screen to flash violently until you go into convulsions on the floor. I think I swallowed my tongue.
I personally like the dread effect, and it certainly adds an interesting dimension to the game. The effect doesn't bother me that much, but I can see when your running away from a mob like that it'd be a HUGE pain.