User blog comment:CNBA3/Aspects of the Great Evils/@comment-24916843-20140518052730

Each aspect both feeds off their respective emotion and grants it to others - demons, angels and humans alike. It can take many forms: like said above, Diablo can instill terror in mortals, but my guess that with him around his demons also become fearless (or perhaps they are afraid of the Lord of Terror much more than of any enemy).

The exact mechanics are unknown, but I'm sure that these emotions are what the Great Evils and Lesser Evils use to corrupt mortals as well. I.e. Diablo used fear to drive Leoric mad (he was so afraid of conspiracies he became paranoid about EVERYTHING), Mephisto used Zakarumites' hatred for evil against themselves, Andariel created the Corrupted Rogues through anguish (maybe those poor girls found all around Act I are those who died before they were... hmmm... persuaded?). Belial lied to his cultists and created illusions so powerful not even The Nephalem could see through those. Azmodan's minions enslaved many people by playing with their sins.

I don't think that without the aspects there is no more (emotion_name) in the world(s), but they are definitely able to manipulate that matter. I think Auriel's imprisonment just allowed Rakanoth to spread his despair uncontested, but the mere fact that she was locked up in a cage did not take all hope away. Similarly, angels were not denied all wisdom when Malthael left for good.

Blizz never gave details, though, and some things are actually hard to figure out. For example, what exactly does the Lord of Destruction title mean? Is he in charge of urge to destroy? Of desire to kill? Of self-destruction? Of primal chaos? He does not seem to wreak more havoc around than any other demon lord would.