Does your world have creatures or beings with true forms that are incomprehensible?
These beings don't have to be divine/godly. It can be anything. Though if you have gods and demons that are like that, I will still accept it.
My Turn:
The Saints are these beings. In order to take on a form that is easy to handle without dying or being driven insane, they have incarnations or avatars as ordinary people who resemble the lesser races. The Saints are gods with true forms that are very incomprehensible. So, they use their incarnations to engage with the lesser races.
The Mechanical Drought is a tricky one because its true form is an eldritch machine in the form of an enormous beast. Some people laid their eyes on it and were driven mad. Though the soul of the Mechanical Drought lies in the body of a young woman.
The Ravakalyn are even more tricky as their true forms aren't incomprehensible, but it is scary looking. What makes their forms incomprehensible is mainly their aura. The Ravakalyn have eldritch aura when they are in their true form. And when they speak, it unleashes a sense of both dread and madness within the unfortunate victim.
The Pillars that fell onto the world are trickier than the Ravakalyn. The longer you stare at the pillars, the more mad you become because there is a countdown that is barely visible on each pillar. The countdown is the same, but the reason behind the countdown is currently unknown. It can lead to an event that could devastate the world. The true form of the pillars aren't incomprehensible, but the meaning behind the countdown is.
What about you?