'Can't comprehend it' works. It's just not something mortal eyes can look at. Consider a few moments of looking at us like staring into the sun for years.

... Or trying to look into a nuclear explosion.

[Nuclear explosions are so tacky, though. If there's one thing he thinks he deserves from credit for, it's being more hands-on in his approach to wiping out humanity. Right?]

Demons are... not quite the same. They were molded by torture in hell, where I'm from. They're human souls twisted into... well. You've probably heard the less pleasant attributes.

[They're some of his best work, those gross little heathens.]