User blog comment:CNBA3/Aspects of the Great Evils/@comment-58609-20140518040830

If I'm correct, you're asking whether things such as terror exist in of themselves, and individuals (e.g. Diablo) are the embodiment of them, or whether Diablo and co. are said to be Lord of X, with "x" being an abstract concept.

To answer that question, I think the implication is that things such as terror (fear), hatred, justice, valour, etc., exist as concepts in of themselves, but the Evils and AC members are tied to the proliferation of that concept, if that makes sense. There are a few cases of this:

1) In 'Book of Cain', Cain reflects that, in his mind, Diablo is the most powerful of the Evils because "as long as Man fears the dark, terror will never die" (or words to that effect). Taking this as true and being literal, terror is a type of force in itself. That force both feeds and is fed by the emotion itself. Diablo is a personification of that force/emotion, and thus, his strength is based on how strong that force/emotion is. In the context of the statement, hatred could be weakened if humanity acted more morally, but fear is a far more instinctive, natural emotion, and thus more insidious, and thus more powerful.

2) There's a precedent for the above point in D1 where (more or less), Diablo gave Albrecht nightmares, Albrecht's fear nourished Diablo. Diablo is feeding off an emotion. An emotion he himself creates, but in the context, something tangible.

3) The same applies for the Angiris Council. In Act IV of D3, prior to Auriel being rescued, all the angels and human inhabitants are consumed by despair. After she's rescued, hope is returned - the difference in the background dialogue in Bastion's Keep instantly changes and becomes more positive. No-one in the keep could have known what had just happened, but on some level, their psychology has been affected.

Granted, none of this is outright fact, but it's hinted as such. The Evils and AC members represent certain forces in Creation, and those forces can be weakned and strengthened. The entity behind them can influence the strength of what they personify, but will also be affected by the strength of the force itself.

Least that's how I see it. Don't take this as an official word though.