I've been giving this question some thought myself, and, thought a little too deeply about it.
I imagined basically the scene from The Dark Knight, where Batman sits down and "interrogates" the Joker.
So I sat down with
Arkhivom.
The conversation between he and I was... interesting. He asked me why I created him. I told him that he was the antithesis to what I believed to be right.
I also told him, that he was both everything I wanted to be, and everything I hated, all mixed into one.
He liked that.
He would.
I told him, that his purpose was to show that there can be some semblance of sanity in that which is undoubtedly pure evil. I told him that, in his own twisted heart, his intentions were no less pure than those most priestly, saintly, and godly. His desire was to bring about something
better. However twisted it might seem to others. However twisted it might seem to
me.
I also told him that, to him, he was not evil. He knew he opposed everything that most everyone else perceived to be
good, but he in no way saw himself as evil. He believed in necessity, and at the risk of quoting Thanos, inevitability.
I explained that to me, in my headcanon, the Celestial Pantheon and the Exodus as described in
Core Lore are
actual events. I simply, do not understand their realty. But, in some way, at least more-so than I do,
he does. He has a beef with the Celestials, and that he thinks they basically downgraded
Arethil with their influence. He wants to wage, essentially, a holy war against all the land to purge this influence, inevitably.
**Edit: I also told him that he has a cool floating castle and a hot demon/dragon bae so he should be thankful.