What I wonder is, why scenario writer(s) considered "terror" to be the most effective one? Why didn't game writer(s) call Diablo as the Lord of Anguish or Hatred? There are 2 other prime evil, and 4 other lesser evils.
the Lord of Lies (Deceit)
the Lord of Sin
the Lord of Pain
the Lord of Anguish
the Lord of Hatred
the Lord of Destruction
Look, game writers could choose 6 other "bad" or "unpleasant" thing. Why do you think did they specifically chose Terror? I think Anguish or Hatred could be more suitable for the most powerful Demon Lord since while terror is instantaneous, anguish and terror lasts longer and torment people more severely. Would you prefer being heavily depressed (by the Lord of Anguish) or terrorized (by the Lord of Terror)? Or Would you prefer being full of hatred (by the Lord of Hatred, which negatively impacts your reason) or being terrorized (by the Lord of Terror)? I think people are more like to prefer being terrorized because it's instantaneous.
I tried to give some silly and overly simplistic examples for the reason that terror is less pleasant. So, if you think alike me, why would be your examples and reasons for the fact that terror is less pleasant?